PRACTICE EXAM 2
The real exam has 60 questions and you are given three hours to complete it. Use the same time limits for this exam. On the real exam, and on all of the exams in this book, give yourself credit only for those questions that you answer 100 percent correctly. For instance, if a question has three correct answers and you get two of the three correct, you get zero credit. There is no partial credit. Good luck!
1. Concerning Java’s Garbage Collector (GC), which are true? (Choose all that apply.)
A. If Object X has a reference to Object Y, then Object Y cannot be GCed.
B. A Java program can request that the GC runs, but such a request does NOT guarantee that the GC will actually run.
C. If the GC decides to delete an object, and if finalize() has never been invoked for that object, it is guaranteed that the GC will invoke finalize() for that object before the object is deleted.
D. Once the GC invokes finalize() on an object, it is guaranteed that the GC will delete that object once finalize() has completed.
E. When the GC runs, it decides whether to remove objects from the heap, the stack, or both.
2. Given:
1. public class BackHanded {
2. int state = 0;
3. BackHanded(int s) { state = s; }
4. public static void main(String... hi) {
5. BackHanded b1 = new BackHanded(1);
6. BackHanded b2 = new BackHanded(2);
7. System.out.println(b1.go(b1) + " " + b2.go(b2));
8. }
9. int go(BackHanded b) {
10. if(this.state == 2) {
11. b.state = 5;
12. go(this);
13. }
14. return ++this.state;
15. } }
What is the result?
A. 1 2
B. 1 3
C. 1 6
D. 1 7
E. 2 6
F. 2 7
G. Compilation fails.
H. An exception is thrown at runtime.
3. Given:
42. String s = "";
43. if(011 == 9) s += 4;
44. if(0x11 == 17) s += 5;
45. Integer I = 12345;
46. if(I.intValue() == Integer.valueOf("12345")) s += 6;
47. System.out.println(s);
What is the result?
A. 5
B. 45
C. 46
D. 56
E. 456
F. Compilation fails.
G. An exception is thrown at runtime.
4. Given:
3. class Sport {
4. Sport play() { System.out.print("play "); return new Sport(); }
5. Sport play(int x) { System.out.print("play x "); return new Sport(); }
6. }
7. class Baseball extends Sport {
8. Baseball play() { System.out.print("baseball "); return new Baseball(); }
9. Sport play(int x) { System.out.print("sport "); return new Sport(); }
10.
11. public static void main(String[] args) {
12. new Baseball().play();
13. new Baseball().play(7);
14. super.play(7);
15. new Sport().play();
16. Sport s = new Baseball();
17. s.play();
18. } }
What is the result?
A. baseball sport sport play play
B. baseball sport play x play sport
C. baseball sport play x play baseball
D. Compilation fails due to a single error.
E. Compilation fails due to errors on more than one line.
5. Given:
2. public class Self extends Thread {
3. public static void main(String[] args) {
4. try {
5. Thread t = new Thread(new Self());
6. t.start();
7. t.start();
8. } catch (Exception e) { System.out.print("e "); }
9. }
10. public void run() {
11. for(int i = 0; i < 2; i++)
12. System.out.print(Thread.currentThread().getName() + " ");
13. } }
Which are true? (Choose all that apply.)
A. Compilation fails.
B. No output is produced.
C. The output could be Thread-1 Thread-1 e
D. The output could be Thread-1 e Thread-1
E. The output could be Thread-1 Thread-1 Thread-2 Thread-2
F. The output could be Thread-1 Thread-2 Thread-1 Thread-2
G. The output could be Thread-1 Thread-1 Thread-1 Thread-1
6. Given:
3. class Stereo { void makeNoise() { assert true; } }
4. public class BoomBox2 extends Stereo {
5. public static void main(String[] args) {
6. new BoomBox2().go(args);
7. }
8. void go(String[] args) {
9. if(args.length > 0) makeNoise();
10. if(args[0].equals("x")) System.out.print("x ");
11. if(args[0] == "x") System.out.println("x2 ");
12. } }
And (if the code compiles), the invocation:
java -ea Boombox2 x
What is the result?
A. x
B. x x2
C. An Error is thrown at runtime.
D. Compilation fails due to an error on line 3.
E. Compilation fails due to an error on line 8.
F. Compilation fails due to an error on line 9.
7. Given:
2. import java.util.*;
3. public class Olives {
4. public static void main(String[] args) {
5. Set<Integer> s = new TreeSet<Integer>();
6. s.add(23); s.add(42); s.add(new Integer(5));
7. Iterator i = s.iterator();
8. // while(System.out.print(i.next())) { }
9. // for(Integer i2: i) System.out.print(i2);
10. // for(Integer i3: s) System.out.print(i3);
11. // while(i.hasNext()) System.out.print(i.get());
12. // while(i.hasNext()) System.out.print(i.next());
13. } }
If lines 8–12 are uncommented, independently, which are true? (Choose all that apply.)
A. Line 8 will compile.
B. Line 9 will compile.
C. Line 10 will compile.
D. Line 11 will compile.
E. Line 12 will compile.
F. Of those that compile, the output will be 23425
G. Of those that compile, the output will be 52342
8. Given the proper import statements and:
23. try {
24. File file = new File("myFile.txt");
25. PrintWriter pw = new PrintWriter(file);
26. pw.println("line 1");
27. pw.close();
28. PrintWriter pw2 = new PrintWriter("myFile.txt");
29. pw2.println("line 2");
30. pw2.close();
31. } catch (IOException e) { }
What is the result? (Choose all that apply.)
A. No file is created.
B. A file named "myFile.txt" is created.
C. Compilation fails due to an error on line 24.
D. Compilation fails due to an error on line 28.
E. "myFile.txt" contains only one line of data, "line 1"
F. "myFile.txt" contains only one line of data, "line 2"
G. "myFile.txt" contains two lines of data, "line 1" then "line 2"
9. Given this code in a method:
3. String s = "-";
4. boolean b = false;
5. int x = 7, y = 8;
6. if((x < 8) ∧ (b = true)) s += "∧";
7. if(!(x > 8) | ++y > 5) s += "|";
8. if(++y > 9 && b == true) s += "&&";
9. if(y % 8 > 1 || y / (x - 7) > 1) s += "%";
10. System.out.println(s);
What is the result?
A. -
B. -|%
C. -∧|%
D. -|&&%
E. -∧|&&%
F. Compilation fails.
G. An exception is thrown at runtime.
10. Given:
3. public class Limits {
4. private int x = 2;
5. protected int y = 3;
6. private static int m1 = 4;
7. protected static int m2 = 5;
8. public static void main(String[] args) {
9. int x = 6; int y = 7;
10. int m1 = 8; int m2 = 9;
11. new Limits().new Secret().go();
12. }
13. class Secret {
14. void go() { System.out.println(x + " " + y + " " + m1 + " " + m2); }
15. } }
What is the result?
A. 2 3 4 5
B. 2 7 4 9
C. 6 3 8 4
D. 6 7 8 9
E. Compilation fails due to multiple errors.
F. Compilation fails due only to an error on line 11.
G. Compilation fails due only to an error on line 14.
11. Note: This question concerns Serialization. As of this writing, the Serialization topic was officially removed from the objectives, BUT we were still getting reports that some testing centers were using versions of the exam that included Serialization questions. If you choose to ignore the Serialization topic, give yourself a free “correct answer” for this question. (FWIW, your authors believe it’s a good topic to understand.)
Given:
3. import java.io.*;
4. class ElectronicDevice { ElectronicDevice() { System.out.print("ed "); }}
5. class Mp3player extends ElectronicDevice implements Serializable {
6. Mp3player() { System.out.print("mp "); }
7. }
8. class MiniPlayer extends Mp3player {
9. MiniPlayer() { System.out.print("mini "); }
10. public static void main(String[] args) {
11. MiniPlayer m = new MiniPlayer();
12. try {
13. FileOutputStream fos = new FileOutputStream("dev.txt");
14. ObjectOutputStream os = new ObjectOutputStream(fos);
15. os.writeObject(m); os.close();
16. FileInputStream fis = new FileInputStream("dev.txt");
17. ObjectInputStream is = new ObjectInputStream(fis);
18. MiniPlayer m2 = (MiniPlayer) is.readObject(); is.close();
19. } catch (Exception x) { System.out.print("x "); }
20. } }
What is the result?
A. ed mp mini
B. ed mp mini ed
C. ed mp mini ed mini
D. ed mp mini ed mp mini
E. Compilation fails.
F. "ed mp mini", followed by an exception.
12. Given:
2. abstract interface Pixie {
3. abstract void sprinkle();
4. static int dust = 3;
5. }
6. abstract class TinkerBell implements Pixie {
7. String fly() { return "flying "; }
8. }
9. public class ForReal extends TinkerBell {
10. public static void main(String[] args) {
11. new ForReal().sprinkle();
12. }
13. public void sprinkle() { System.out.println(fly() + " " + dust); }
14. }
What is the result? (Choose all that apply.)
A. flying 3
B. Compilation fails because TinkerBell doesn’t properly implement Pixie.
C. Compilation fails because ForReal doesn’t properly extend TinkerBell.
D. Compilation fails because Pixie is not a legal interface.
E. Compilation fails because ForReal doesn’t properly implement Pixie.
F. Compilation fails because TinkerBell is not a legal abstract class.
13. Given:
2. public class Errrrr {
3. static String a = null;
4. static String s = "";
5. public static void main(String[] args) {
6. try {
7. a = args[0];
8. System.out.print(a);
9. s += "t1 ";
10. }
11. catch (RuntimeException re) { s += "c1 "; }
12. finally { s += "f1 "; }
13. System.out.println(" " + s);
14. } }
And two command-line invocations:
java Errrrr
java Errrrr x
What is the result?
A. First: f1, then: x t1
B. First: f1, then: x t1 f1
C. First: c1, then: x t1
D. First: c1, then: x t1 f1
E. First: c1 f1, then: x t1
F. First: c1 f1, then: x t1 f1
G. Compilation fails.
14. Given:
51. String s = "4.5x4.a.3";
52. String[] tokens = s.split("\s");
53. for(String o: tokens)
54. System.out.print(o + " ");
55.
56. System.out.print(" ");
57. tokens = s.split("\..");
58. for(String o: tokens)
59. System.out.print(o + " ");
What is the result?
A. 4 x4
B. 4 x4 .
C. 4 x4 3
D. 4 5x4 a 3 4 x4
E. 4.5x4.a.3 4 x4
F. 4.5x4.a.3 4 x4 .
15. Given:
2. abstract class Tool {
3. int SKU;
4. abstract void getSKU();
5. }
6. public class Hammer {
7. // insert code here
8. }
Which line(s), inserted independently at line 7, will compile? (Choose all that apply.)
A. void getSKU() { ; }
B. private void getSKU() { ; }
C. protected void getSKU() { ; }
D. public void getSKU() { ; }
16. Given:
3. public class Stubborn implements Runnable {
4. static Thread t1;
5. static int x = 5;
6. public void run() {
7. if(Thread.currentThread().getId() == t1.getId()) shove();
8. else push();
9. }
10. static synchronized void push() { shove(); }
11. static void shove() {
12. synchronized(Stubborn.class) {
13. System.out.print(x-- + " ");
14. try { Thread.sleep(2000); } catch (Exception e) { ; }
15. if(x > 0) push();
16. } }
17. public static void main(String[] args) {
18. t1 = new Thread(new Stubborn());
19. t1.start();
20. new Thread(new Stubborn()).start();
21. } }
Which are true? (Choose all that apply.)
A. Compilation fails.
B. The output is 5 4 3 2 1
C. The output is 5 4 3 2 1 0
D. The program could deadlock.
E. The output could be 5, followed by deadlock.
F. If the sleep() invocation was removed, the chance of deadlock would decrease.
G. As it stands, the program can’t deadlock, but if shove() was changed to synchronized, then the program could deadlock.
17. Given:
2. class Super {
3. static String os = "";
4. void doStuff() { os += "super "; }
5. }
6. public class PolyTest extends Super {
7. public static void main(String[] args) { new PolyTest().go(); }
8. void go() {
9. Super s = new PolyTest();
10. PolyTest p = (PolyTest)s;
11. p.doStuff();
12. s.doStuff();
13. p.doPoly();
14. s.doPoly();
15. System.out.println(os);
16. }
17. void doStuff() { os += "over "; }
18. void doPoly() { os += "poly "; }
19. }
What is the result?
A. Compilation fails.
B. over over poly poly
C. over super poly poly
D. super super poly poly
E. An exception is thrown at runtime.
18. Given two files:
1. package com.wickedlysmart;
2. import com.wickedlysmart2.*;
3. public class Launcher {
4. public static void main(String[] args) {
5. Utils u = new Utils();
6. u.do1();
7. u.do2();
8. u.do3();
9. } }
and the correctly compiled and located:
1. package com.wickedlysmart2;
2. class Utils {
3. void do1() { System.out.print("do1 "); }
4. protected void do2() { System.out.print("do2 "); }
5. public void do3() { System.out.print("do3 "); }
6. }
What is the result for Launcher? (Choose all that apply.)
A. do1 do2 do3
B. "do1 ", followed by an exception
C. Compilation fails due to an error on line 5 of Launcher.
D. Compilation fails due to an error on line 6 of Launcher.
E. Compilation fails due to an error on line 7 of Launcher.
F. Compilation fails due to an error on line 8 of Launcher.
19. Given:
2. public class Wacky {
3. public static void main(String[] args) {
4. int x = 5;
5. int y = (x < 6) ? 7 : 8;
6. System.out.print(y + " ");
7. boolean b = (x < 6) ? false : true;
8. System.out.println(b + " ");
9. assert(x < 6) : "bob";
10. assert( ((x < 6) ? false : true) ) : "fred";
11. } }
And, if the code compiles, the invocation:
java -ea Wacky
Which will be contained in the output? (Choose all that apply.)
A. 7
B. 8
C. bob
D. fred
E. true
F. false
G. Compilation fails.
20. Given:
3. class MotorVehicle {
4. protected int doStuff(int x) { return x * 2; }
5. }
6. class Bicycle {
7. void go(MotorVehicle m) {
8. System.out.print(m.doStuff(21) + " ");
9. } }
10. public class Beemer extends MotorVehicle {
11. public static void main(String[] args) {
12. System.out.print(new Beemer().doStuff(11) + " ");
13. new Bicycle().go(new Beemer());
14. new Bicycle().go(new MotorVehicle());
15. }
16. int doStuff(int x) { return x * 3; }
17. }
What is the result? (Choose all that apply.)
A. 22 42 42
B. 22 63 63
C. 33 42 42
D. 33 63 42
E. Compilation fails.
F. An exception is thrown at runtime.
21. Which are true? (Choose all that apply.)
A. A single JAR file can contain only files from a single package.
B. A JAR file can be used only on the machine on which it was created.
C. When javac is using files within a JAR file, it will unJAR the file during compilation.
D. The Java SDK installation directory tree on a Java developer’s computer usually includes a subdirectory tree named jre/lib/ext.
E. A JAR file is structured so that all the files and directories that you’ve “JARed” will be subdirectory(ies) of the META-INF directory.
F. When javac is invoked with a classpath option, and you need to find files in a JAR file, the name of the JAR file must be included at the end of the path.
22. Given the proper import(s), and given:
13. class NameCompare implements Comparator<Stuff> {
14. public int compare(Stuff a, Stuff b) {
15. return b.name.compareTo(a.name);
16. } }
18. class ValueCompare implements Comparator<Stuff> {
19. public int compare(Stuff a, Stuff b) {
20. return (a.value - b.value);
21. } }
Which are true? (Choose all that apply.)
A. This code does not compile.
B. This code allows you to use instances of Stuff as keys in Maps.
C. These two classes properly implement the Comparator interface.
D. NameCompare allows you to sort a collection of Stuff instances alphabetically.
E. ValueCompare allows you to sort a collection of Stuff instances in ascending numeric order.
F. If you changed both occurrences of "compare()" to "compareTo()", the code would compile.
23. Given:
3. public class Chopper {
4. String a = "12b";
5. public static void main(String[] args) {
6. System.out.println(new Chopper().chop(args[0]));
7. }
8. int chop(String a) {
9. if(a == null) throw new IllegalArgumentException();
10. return Integer.parseInt(a);
11. } }
And, if the code compiles, the invocation:
java Chopper
What is the result?
A. 12
B. 12b
C. Compilation fails.
D. A NullPointerException is thrown.
E. A NumberFormatException is thrown.
F. An IllegalArgumentException is thrown.
G. An ArrayIndexOutOfBoundsException is thrown.
24. Which, concerning command-line options, are true? (Choose all that apply.)
A. The -D flag is used in conjunction with a name-value pair.
B. The -D flag can be used with javac to set a system property.
C. The -d flag can be used with java to disable assertions.
D. The -d flag can be used with javac to specify where to place .class files.
E. The -d flag can be used with javac to document the locations of deprecated APIs in source files.
25. Given that "it, IT" is the locale code for Italy and that "pt, BR" is the locale code for Brazil, and given:
51. Date d = new Date();
52. DateFormat df = DateFormat.getDateInstance(DateFormat.FULL);
53. Locale[] la = {new Locale("it", "IT"), new Locale("pt", "BR")};
54. for(Locale l: la) {
55. df.setLocale(l);
56. System.out.println(df.format(d));
57. }
Which are true? (Choose all that apply.)
A. An exception is thrown at runtime.
B. Compilation fails due to an error on line 53.
C. Compilation fails due to an error on line 55.
D. Compilation fails due to an error on line 56.
E. The output will contain only today’s date for the Italian locale.
F. The output will contain today’s date for both Italian and Brazilian locales.
26. Given this code in a method:
4. Integer[][] la = {{1,2}, {3,4,5}};
5. Number[] na = la[1];
6. Number[] na2 = (Number[])la[0];
7. Object o = na2;
8. la[1] = (Number[])o;
9. la[0] = (Integer[])o;
What is the result? (Choose all that apply.)
A. Compilation succeeds.
B. Compilation fails due to an error on line 4.
C. Compilation fails due to an error on line 5.
D. Compilation fails due to an error on line 6.
E. Compilation fails due to an error on line 7.
F. Compilation fails due to an error on line 8.
G. Compilation fails due to an error on line 9.
H. Compilation succeeds but an exception is thrown at runtime.
27. Given:
3. public class Ice {
4. Long[] stockings = {new Long(3L), new Long(4L), new Long(5L)};
5. static int count = 0;
6. public static void main(String[] args) {
7. new Ice().go();
8. System.out.println(count);
9. }
10. void go() {
11. for(short x = 0; x < 5; x++) {
12. if(x == 2) return;
13. for(long ell: stockings) {
14. count++;
15. if(ell == 4) break;
16. } } } }
What is the result? (Choose all that apply.)
A. 2
B. 4
C. 8
D. 12
E. Compilation fails due to an error on line 13.
F. Compilation fails due to an error on line 16.
28. Given the proper import statement(s) and:
4. Console c = System.console();
5. char[] pw;
6. if(c == null) return;
7. pw = c.readPassword("%s", "pw: ");
8. System.out.println(c.readLine("%s", "input: "));
Which statements are true? (Choose all that apply.)
A. An exception will be thrown on line 8.
B. The variable pw must be a String, not a char[].
C. No import statements are necessary for the code to compile.
D. If the code compiles and is invoked, line 7 might never run.
E. Without a third argument, the readPassword() method will echo the password the user types.
F. If line 4 was replaced with the following code, the program would still compile: "Console c = new Console();".
29. Given that:
Exception is the superclass of IOException, and
IOException is the superclass of FileNotFoundException, and
3. import java.io.*;
4. class Physicist {
5. void think() throws IOException { }
6. }
7. public class Feynman extends Physicist {
8. public static void main(String[] args) {
9. new Feynman().think();
10. }
11. // insert method here
12. }
Which of the following methods, inserted independently at line 11, compiles? (Choose all that apply.)
A. void think() throws Exception { }
B. void think() throws FileNotFoundException { }
C. public void think() { }
D. protected void think() throws IOException { }
E. private void think() throws IOException { }
F. void think() { int x = 7/0; }
30. Given:
4. public class Zingseng extends Thread {
5. public static void main(String[] args) throws Exception {
6. Thread t1 = new Thread(new Zingseng());
7. t1.start();
8. // insert code here
9. for(int i = 0; i < 1000; i++) // Loop #1
10. System.out.print(Thread.currentThread().getName() + " ");
11. }
12. public void run() {
13. for(int i = 0; i < 1000; i++) // Loop #2
14. System.out.print(Thread.currentThread().getName() + " ");
15. } }
Which code, inserted independently at line 8, will make most (or all) of Loop #2’s iterations run before most (or all) of Loop #1’s iterations? (Choose all that apply.)
A. // just a comment
B. t1.join();
C. t1.yield();
D. t1.sleep(1000);
31. Given:
2. public class Kant extends Philosopher {
3. // insert code here
5. public static void main(String[] args) {
6. new Kant("Homer");
7. new Kant();
8. }
9. }
10. class Philosopher {
11. Philosopher(String s) { System.out.print(s + " "); }
12. }
Which set(s) of code, inserted independently at line 3, produce the output "Homer Bart"? (Choose all that apply.)
A. Kant() { this("Bart"); }
Kant(String s) { super(s); }
B. Kant() { super("Bart"); }
Kant(String s) { super(s); }
C. Kant() { super(); }
Kant(String s) { super(s); }
D. Kant() { super("Bart"); }
Kant(String s) { this(); }
E. Kant() { super("Bart"); }
Kant(String s) { this("Homer"); }
32. Given:
2. public class Epoch {
3. static int jurassic = 0;
4. public static void main(String[] args) {
5. assert(doStuff(5));
6. }
7. static boolean doStuff(int x) {
8. jurassic += x;
9. return true;
10. } }
Which are true? (Choose all that apply.)
A. The code compiles using javac -ea Epoch.java
B. The assert statement on line 5 is used appropriately.
C. The code compiles using javac -source 1.3 Epoch.java
D. The code compiles using javac -source 1.4 Epoch.java
E. The code compiles using javac -source 1.6 Epoch.java
F. The code will not compile using any version of the javac compiler.
33. Given
1. public class Kaput {
2. Kaput myK;
3. String degree = "0";
4. public static void main(String[] args) {
5. Kaput k1 = new Kaput();
6. go(k1);
7. System.out.println(k1.degree);
8. }
9. static Kaput go(Kaput k) {
10. final Kaput k1 = new Kaput();
11. k.myK = k1;
12. k.myK.degree = "7";
13. return k.myK;
14. } }
What is the result?
A. 0
B. 7
C. null
D. Compilation fails.
E. An exception is thrown at runtime.
34. Given:
3. class Holder {
4. enum Gas { ARGON, HELIUM };
5. }
6. public class Basket extends Holder {
7. public static void main(String[] args) {
8. short s = 7; long l = 9L; float f = 4.0f;
9. int i = 3; char c = 'c'; byte b = 5;
10. // insert code here
11. default: System.out.println("howdy");
12. } } }
Which line(s) of code (if any), inserted independently at line 10, will compile? (Choose all that apply.)
A. switch (s) {
B. switch (l) {
C. switch (f) {
D. switch (i) {
E. switch (c) {
F. switch (b) {
G. switch (Gas.ARGON) {
H. The code will not compile due to additional error(s).
35. Given
2. class Horse {
3. static String s = "";
4. void beBrisk() { s += "trot "; }
5. }
6. public class Andi extends Horse {
7. void beBrisk() { s += "tolt "; }
8. public static void main(String[] args) {
9. Horse x0 = new Horse();
10. Horse x1 = new Andi(); x1.beBrisk();
11. Andi x2 = (Andi)x1; x2.beBrisk();
12. Andi x3 = (Andi)x0; x3.beBrisk();
13. System.out.println(s);
14. } }
What is the result?
A. tolt tolt tolt
B. trot tolt trot
C. trot tolt tolt
D. Compilation fails.
E. An exception is thrown at runtime.
36. Given:
3. class Tire {
4. private static int x = 6;
5. public static class Wheel {
6. void go() { System.out.print("roll " + x++); }
7. } }
8. public class Car {
9. public static void main(String[] args) {
10. // insert code here
11. } }
And the three code fragments:
I. new Tire.Wheel().go();
II. Tire t = new Tire(); t.Wheel().go();
III. Tire.Wheel w = new Tire.Wheel(); w.go();
Assuming we insert a single fragment at line 10, which are true? (Choose all that apply.)
A. Once compiled, the output will be "roll 6"
B. Once compiled, the output will be "roll 7"
C. Fragment I, inserted at line 10, will compile.
D. Fragment II, inserted at line 10, will compile.
E. Fragment III, inserted at line 10, will compile.
F. Taken separately, class Tire will not compile on its own.
37. Given:
3. public class Fortran {
4. static int bump(int i) { return i + 2; }
5. public static void main(String[] args) {
6. for(int x = 0; x < 5; bump(x))
7. System.out.print(x + " ");
8. } }
What is the result?
A. 2 4
B. 0 2 4
C. 2 4 6
D. 0 2 4 6
E. Compilation fails.
F. Some other result occurs.
38. You need the three classes and/or interfaces to work together to produce the output "Kara Charis". Fill in the blanks using the following fragments so the correct is-a and has-a relationships are established to produce this output. Note: You may not need to fill in every empty blank space, but a blank space can hold only one fragment. Also note that not all the fragments will be used, and that fragments CAN be used more than once.
Code to complete:
Fragments:
39. Given:
1. import java.util.*;
2. public class PirateTalk {
3. public static void main(String... arrrrgs) {
4. Properties p = System.getProperties();
5. p.setProperty("pirate", "scurvy");
6. String s = p.getProperty("argProp") + " ";
7. s += p.getProperty("pirate");
8. System.out.println(s);
9. } }
And the command-line invocation:
java PirateTalk -DargProp="dog,"
What is the result?
A. dog, scurvy
B. null scurvy
C. scurvy dog,
D. scurvy null
E. Compilation fails.
F. An exception is thrown at runtime.
G. An “unrecognized option” command-line error is thrown.
40. Given:
2. import java.util.*;
3. public class VLA implements Comparator<VLA> {
4. int dishSize;
5. public static void main(String[] args) {
6. VLA[] va = {new VLA(40), new VLA(200), new VLA(60)};
7.
8. for(VLA v: va) System.out.print(v.dishSize + " ");
9. int index = Arrays.binarySearch(va, new VLA(60), va[0]);
10. System.out.print(index + " ");
11. Arrays.sort(va);
12. for(VLA v: va) System.out.print(v.dishSize + " ");
13. index = Arrays.binarySearch(va, new VLA(60), va[0]);
14. System.out.println(index);
15. }
16. public int compare(VLA a, VLA b) {
17. return a.dishSize - b.dishSize;
18. }
19. VLA(int d) { dishSize = d; }
20. }
Which result is most likely?
A. Compilation fails.
B. "40 200 60 2 40 60 200 1"
C. "40 200 60 -2 40 60 200 1"
D. "40 200 60", followed by an exception.
E. "40 200 60 -2", followed by an exception.
41. Given:
2. class RainCatcher {
3. static StringBuffer s;
4. public static void main(String[] args) {
5. Integer i = new Integer(42);
6. for(int j = 40; j < i; i--)
7. switch(i) {
8. case 41: s.append("41 ");
9. default: s.append("def ");
10. case 42: s.append("42 ");
11. }
12. System.out.println(s);
13. } }
What is the result?
A. 41 def
B. 41 def 42
C. 42 41 def 42
D. An exception is thrown at runtime.
E. Compilation fails due to an error on line 6.
F. Compilation fails due to an error on line 7.
42. Given:
2. import java.util.*;
3. class Snack {
4. static List<String> s1 = new ArrayList<String>();
5. }
6. public class Chips extends Snack {
7. public static void main(String[] args) {
8. List c1 = new ArrayList();
9. s1.add("1"); s1.add("2");
10. c1.add("3"); c1.add("4");
11. getStuff(s1, c1);
12. }
13. static void getStuff(List<String> a1, List a2) {
14. for(String s1: a1) System.out.print(s1 + " ");
15. for(String s2: a2) System.out.print(s2 + " ");
16. } }
What is the result? (Choose all that apply.)
A. "1 2 3 4"
B. "1 2", followed by an exception
C. An exception is thrown with no other output.
D. Compilation fails due to an error on line 13.
E. Compilation fails due to an error on line 14.
F. Compilation fails due to an error on line 15.
43. Given that Calendar.MONTH starts with January == 0, and given:
3. import java.util.*;
4. public class Wise {
5. public static void main(String[] args) {
6. Calendar c = Calendar.getInstance();
7. c.set(1999,11,25);
8. c.roll(Calendar.MONTH, 3);
9. c.add(Calendar.DATE, 10);
10. System.out.println(c.getTime());
11. } }
And, if the program compiles, what date is represented in the output?
A. March 4, 1999
B. April 4, 1999
C. March 4, 2000
D. April 4, 2000
E. Compilation fails.
F. An exception is thrown at runtime.
44. Given the following two files containing Light.java and Dark.java:
2. package ec.ram;
3. public class Light{}
4. class Burn{}
2. package ec.ram;
3. public class Dark{}
4. class Melt{}
And if those two files are located in the following directory structure:
And the following commands are executed, in order, from the ROOT directory:
javac Light.java -cp checker/dira -d checker/dirb
javac Dark.java -cp checker/dirb -d checker/dira
jar -cf checker/dira/a.jar checker
A new JAR file is created after executing the above commands. Which of the following files will exist inside that JAR file? (Choose all that apply.)
A. [JAR]/dira/ec/ram/Melt.class
B. [JAR]/checker/dirb/ec/ram/Burn.class
C. [JAR]/dirb/ec/ram/Melt.class
D. [JAR]/checker/dira/ec/ram/Burn.class
E. [JAR]/dira/a.jar
F. [JAR]/checker/dira/a.jar
45. Given:
42. String s1 = " ";
43. StringBuffer s2 = new StringBuffer(" ");
44. StringBuilder s3 = new StringBuilder(" ");
45. for(int i = 0; i < 1000; i++) // Loop #1
46. s1 = s1.concat("a");
47. for(int i = 0; i < 1000; i++) // Loop #2
48. s2.append("a");
49. for(int i = 0; i < 1000; i++) // Loop #3
50. s3.append("a");
Which statements will typically be true? (Choose all that apply.)
A. Compilation fails.
B. Loop #3 will tend to execute faster than Loop #2.
C. Loop #1 will tend to use less memory than the other two loops.
D. Loop #1 will tend to use more memory than the other two loops.
E. All three loops will tend to use about the same amount of memory.
F. In order for this code to compile, the java.util package is required.
G. If multiple threads need to use an object, the s2 object should be safer than the s3 object.
46. Given:
2. public class Payroll {
3. int salary;
4. int getSalary() { return salary; }
5. void setSalary(int s) {
6. assert(s > 30000);
7. salary = s;
8. } }
Which are true? (Choose all that apply.)
A. Compilation fails.
B. The class is well encapsulated as it stands.
C. Removing line 6 would weaken the class’s degree of cohesion.
D. Removing line 6 would weaken the class’s degree of encapsulation.
E. If the salary variable was private, the class would be well encapsulated.
F. Removing line 6 would make the class’s use of assertions more appropriate.
47. Given:
1. class GardenTool {
2. static String s = "";
3. String name = "Tool ";
4. GardenTool(String arg) { this(); s += name; }
5. GardenTool() { s += "gt "; }
6. }
7. public class Rake extends GardenTool {
8. { name = "Rake "; }
9. Rake(String arg) { s += name; }
10. public static void main(String[] args) {
11. new GardenTool("hey ");
12. new Rake("hi ");
13. System.out.println(s);
14. }
15. { name = "myRake "; }
16. }
What is the result?
A. Tool Rake
B. Tool myRake
C. gt Tool Rake
D. gt Tool myRake
E. gt Tool gt Rake
F. gt Tool gt myRake
G. gt Tool gt Tool myRake
H. Compilation fails.
48. Given:
3. public class Race {
4. public static void main(String[] args) {
5. Horse h = new Horse();
6. Thread t1 = new Thread(h, "Andi");
7. Thread t2 = new Thread(h, "Eyra");
8. new Race().go(t2);
9. t1.start();
10. t2.start();
11. }
12. void go(Thread t) { t.start(); }
13. }
14. class Horse implements Runnable {
15. public void run() {
16. System.out.print(Thread.currentThread().getName() + " ");
17. } }
What is the result? (Choose all that apply.)
A. Compilation fails.
B. No output is produced.
C. The output could be: "Andi Eyra "
D. The output could be: "Eyra Andi Eyra "
E. The output could be: "Eyra ", followed by an exception.
F. The output could be: "Eyra Andi ", followed by an exception.
49. Given the proper import statement(s) and given:
4. Map<String, String> h = new Hashtable<String, String>();
5. String[] k = {"1", "2", "3", null};
6. String[] v = {"a", "b", null, "d"};
7.
8. for(int i=0; i<4; i++) {
9. h.put(k[i], v[i]);
10. System.out.print(h.get(k[i]) + " ");
11. }
12. System.out.print(h.size() + " " + h.values() + "
");
What result is most likely?
A. Compilation fails.
B. "a b d 3 [b, d, a]"
C. "a b null d 3 [b, d, a]"
D. "a b null d 4 [b, d, null, a]"
E. "a b", followed by an exception.
F. "a b null", followed by an exception.
50. Given:
3. public class Fiji {
4. static Fiji base;
5. Fiji f;
6. public static void main(String[] args) {
7. new Fiji().go();
8. // do more stuff
9. }
10. void go() {
11. Fiji f1 = new Fiji();
12. base = f1;
13. Fiji f2 = new Fiji();
14. f1.f = f2;
15. Fiji f3 = f1.f;
16. f2.f = f1;
17. base = null; f1 = null; f2 = null;
18. // do stuff
19. } }
Which are true? (Choose all that apply.)
A. At line 8, one object is eligible for garbage collection.
B. At line 8, two objects are eligible for garbage collection.
C. At line 8, three objects are eligible for garbage collection.
D. At line 18, 0 objects are eligible for garbage collection.
E. At line 18, two objects are eligible for garbage collection.
F. At line 18, three objects are eligible for garbage collection.
51. Your company makes compute-intensive, 3D rendering software for the movie industry. Your chief scientist has just discovered a new algorithm for several key methods in a commonly used utility class. The new algorithm will decrease processing time by 15 percent, without having to change any method signatures. After you change these key methods, and in the course of rigorous system testing, you discover that the changes have introduced no new bugs into the software.
In terms of your software’s overall design, which are probably true? (Choose all that apply.)
A. Your software is well encapsulated.
B. Your software demonstrated low cohesion.
C. Your software demonstrated high cohesion.
D. Your software demonstrated loose coupling.
E. Your software demonstrated tight coupling.
52. Which are true about the classes and interfaces in java.util? (Choose all that apply.)
A. LinkedHashSet is-a Collection.
B. Vector is-a List.
C. LinkedList is-a Queue.
D. LinkedHashMap is-a Collection.
E. TreeMap is-a SortedMap.
F. Queue is-a Collection.
G. Hashtable is-a Set.
53. Given that File.createNewFile() throws IOException, and that FileNotFoundException extends IOException, use the following fragments to fill in the blanks so that the code compiles. You must use all the fragments, and each fragment can be used only once. Note: As in the real exam, some drag-and-drop style questions might have several correct answers. You will receive full credit for ANY one of the correct answers.
import java.io.*;
public class SticksMud {
public static void main(String[] args) {
try {
File dir = new File("dir");
dir.createNewFile();
}
} }
Fragments:
54. Given:
2. class Grandfather {
3. static String name = "gf ";
4. String doStuff() { return "grandf "; }
5. }
6. class Father extends Grandfather {
7. static String name = "fa ";
8. String doStuff() { return "father "; }
9. }
10. public class Child extends Father {
11. static String name = "ch ";
12. String doStuff() { return "child "; }
13. public static void main(String[] args) {
14. Father f = new Father();
15. System.out.print(((Grandfather)f).name
+ ((Grandfather)f).doStuff()) ;
16. Child c = new Child();
17. System.out.println(((Grandfather)c).name
+ ((Grandfather)c).doStuff() + ((Father)c).doStuff());
18. } }
What is the result? (Choose all that apply.)
A. Compilation fails.
B. fa father ch child child
C. gf father gf child child
D. fa grandf ch grandf father
E. gf grandf gf grandf father
F. An exception is thrown at runtime.
55. Given:
1. class MyClass { }
And given that MyClass2 has properly overridden equals() and hashCode(), objects from which classes make good hashing keys? (Choose all that apply.)
A. MyClass
B. MyClass2
C. java.lang.String
D. java.lang.Integer
E. java.lang.StringBuilder
56. Given:
2. public class Buffalo {
3. static int x;
4. int y;
5. public static int getX() { return x; }
6. public static void setX(int newX) { x = newX; }
7. public int getY() { return y; }
8. public void setY(int newY) { y = newY; }
9. }
Which lines of code need to be changed to make the class thread safe? (Choose all that apply.)
A. Line 2
B. Line 3
C. Line 4
D. Line 5
E. Line 6
F. Line 7
G. Line 8
57. Given:
2. class Animal { }
3. class Dog extends Animal { }
4. class Cat extends Animal { }
5. public class Mixer<A extends Animal> {
6. public <C extends Cat> Mixer<? super Dog> useMe(A a, C c) {
7. //Insert Code Here
8. } }
Which, inserted independently at line 7, compile? (Choose all that apply.)
A. return null;
B. return new Mixer<Dog>();
C. return new Mixer<Animal>();
D. return new Mixer<A>();
E. return new Mixer<a>();
F. return new Mixer<c>();
58. Given:
2. class Chilis {
3. Chilis(String c, int h) { color = c; hotness = h; }
4. String color;
5. private int hotness;
6. public boolean equals(Object o) {
7. Chilis c = (Chilis)o;
8. if(color.equals(c.color) && (hotness == c.hotness)) return true;
9. return false;
10. }
11. // insert code here
12. }
Which, inserted independently at line 11, fulfill the equals() and hashCode() contract for Chilis? (Choose all that apply.)
A. public int hashCode() { return 7; }
B. public int hashCode() { return hotness; }
C. public int hashCode() { return color.length(); }
D. public int hashCode() { return (int)(Math.random() * 200); }
E. public int hashCode() { return (color.length() + hotness); }
59. Given the proper import(s), and this code in a method:
4. List<String> x = new LinkedList<String>();
5. Set<String> hs = new HashSet<String>();
6. String[] v = {"a", "b", "c", "b", "a"};
7. for(String s: v) {
8. x.add(s); hs.add(s);
9. }
10. System.out.print(hs.size() + " " + x.size() + " ");
11. HashSet hs2 = new HashSet(x);
12. LinkedList x2 = new LinkedList(hs);
13. System.out.println(hs2.size() + " " + x2.size());
What is the result?
A. 3 3 3 3
B. 3 5 3 3
C. 3 5 3 5
D. 5 5 3 3
E. 5 5 5 5
F. Compilation fails.
G. An exception is thrown at runtime.
60. Given the proper import(s), and given:
4. public static void main(String[] args) {
5. List<Integer> x = new ArrayList<Integer>();
6. x.add(new Integer(3));
7. doStuff(x);
8. for(Integer i: x)
9. System.out.print(i + " ");
10. }
11. static void doStuff(List y) {
12. y.add(new Integer(4));
13. y.add(new Float(3.14f));
14. }
What is the result? (Choose all that apply.)
A. Compilation fails.
B. The output will be "4 "
C. The output will be "3 4 "
D. The output will be "3 4 3.14 "
E. The output will be "3 3.14 4 "
F. The output will be "3 4 ", followed by an exception.
G. An exception will be thrown before any output is produced.
Quick Answer Key
1. B, C
2. F
3. E
4. D
5. C, D
6. C
7. C, E, G
8. B, F
9. D
10. A
11. B
12. A
13. F
14. E
15. A, B, C, D
16. C
17. A
18. C, D, E, F
19. A, D, F
20. E
21. D, F
22. C, E
23. G
24. A, D
25. C
26. F
27. B
28. D
29. B, C, D, F
30. B, D
31. A, B
32. D, E
33. A
34. A, D, E, F, G
35. E
36. A, C, E
37. F
38. Drag and Drop
39. B
40. E
41. D
42. F
43. B
44. B
45. B, D, G
46. E, F
47. F
48. E, F
49. E
50. C, D
51. A, D
52. A, B, C, E, F
53. Drag and Drop
54. C
55. B, C, D
56. B through G
57. A, B, C
58. A, B, C, E
59. B
60. F
PRACTICE EXAM 2: ANSWERS
1. Concerning Java’s Garbage Collector (GC), which are true? (Choose all that apply.)
A. If Object X has a reference to Object Y, then Object Y cannot be GCed.
B. A Java program can request that the GC runs, but such a request does NOT guarantee that the GC will actually run.
C. If the GC decides to delete an object, and if finalize() has never been invoked for that object, it is guaranteed that the GC will invoke finalize() for that object before the object is deleted.
D. Once the GC invokes finalize() on an object, it is guaranteed that the GC will delete that object once finalize() has completed.
E. When the GC runs, it decides whether to remove objects from the heap, the stack, or both.
Answer (for Objective 7.4):
B and C are correct.
A is incorrect because if no Object has a reference to Object X, then both X and Y can be GCed. D is incorrect because it’s possible for finalize() to send a reference to itself back to an object in a live thread, making the GC candidate “ineligible” for GC. E is incorrect because the GC never touches the stack.
2. Given:
1. public class BackHanded {
2. int state = 0;
3. BackHanded(int s) { state = s; }
4. public static void main(String... hi) {
5. BackHanded b1 = new BackHanded(1);
6. BackHanded b2 = new BackHanded(2);
7. System.out.println(b1.go(b1) + " " + b2.go(b2));
8. }
9. int go(BackHanded b) {
10. if(this.state == 2) {
11. b.state = 5;
12. go(this);
13. }
14. return ++this.state;
15. } }
What is the result?
A. 1 2
B. 1 3
C. 1 6
D. 1 7
E. 2 6
F. 2 7
G. Compilation fails.
H. An exception is thrown at runtime.
Answer (for Objective 7.3):
F is correct. There are only two BackHanded objects. The first call to go() is pretty straightforward, but don’t get confused; "b" and "this" are referring to the same object. The second call to go() is a little trickier—the "if" test is true, so go() is invoked a third time. The result of the third invocation would be 6, but it’s not kept. When control is returned to the second invocation of go(), state (from the same object) is incremented again, to 7.
A, B, C, D, E, G, and H are incorrect based on the above.
3. Given:
42. String s = "";
43. if(011 == 9) s += 4;
44. if(0x11 == 17) s += 5;
45. Integer I = 12345;
46. if(I.intValue() == Integer.valueOf("12345")) s += 6;
47. System.out.println(s);
What is the result?
A. 5
B. 45
C. 46
D. 56
E. 456
F. Compilation fails.
G. An exception is thrown at runtime.
Answer (for Objective 3.1):
E is correct. Line 43 is comparing an octal int to an int. Line 44 is comparing a hexadecimal int to an int. Line 46 is comparing an int to an Integer, which is unboxed before the comparison is made.
A, B, C, D, F, and G are incorrect based on the above.
4. Given:
3. class Sport {
4. Sport play() { System.out.print("play "); return new Sport(); }
5. Sport play(int x) { System.out.print("play x "); return new Sport(); }
6. }
7. class Baseball extends Sport {
8. Baseball play() { System.out.print("baseball "); return new Baseball(); }
9. Sport play(int x) { System.out.print("sport "); return new Sport(); }
10.
11. public static void main(String[] args) {
12. new Baseball().play();
13. new Baseball().play(7);
14. super.play(7);
15. new Sport().play();
16. Sport s = new Baseball();
17. s.play();
18. } }
What is the result?
A. baseball sport sport play play
B. baseball sport play x play sport
C. baseball sport play x play baseball
D. Compilation fails due to a single error.
E. Compilation fails due to errors on more than one line.
Answer (for Objective 1.4):
D is correct. The only error is on line 14: A call to super cannot be made from a static context. The overridden play() method on line 8 is an example of a covariant return, which is a legal override as of Java 5.
A, B, C, and E are incorrect based on the above.
5. Given:
2. public class Self extends Thread {
3. public static void main(String[] args) {
4. try {
5. Thread t = new Thread(new Self());
6. t.start();
7. t.start();
8. } catch (Exception e) { System.out.print("e "); }
9. }
10. public void run() {
11. for(int i = 0; i < 2; i++)
12. System.out.print(Thread.currentThread().getName() + " ");
13. } }
Which are true? (Choose all that apply.)
A. Compilation fails.
B. No output is produced.
C. The output could be Thread-1 Thread-1 e
D. The output could be Thread-1 e Thread-1
E. The output could be Thread-1 Thread-1 Thread-2 Thread-2
F. The output could be Thread-1 Thread-2 Thread-1 Thread-2
G. The output could be Thread-1 Thread-1 Thread-1 Thread-1
Answer (for Objective 4.1):
C and D are correct. When you attempt to invoke start() on the same thread more than once, an exception is thrown and a second thread is NOT started. That exception doesn’t keep the first thread from completing.
A, B, E, F, and G are incorrect based on the above.
6. Given:
3. class Stereo { void makeNoise() { assert true; } }
4. public class BoomBox2 extends Stereo {
5. public static void main(String[] args) {
6. new BoomBox2().go(args);
7. }
8. void go(String[] args) {
9. if(args.length > 0) makeNoise();
10. if(args[0].equals("x")) System.out.print("x ");
11. if(args[0] == "x") System.out.println("x2 ");
12. } }
And (if the code compiles), the invocation:
java -ea Boombox2 x
What is the result?
A. x
B. x x2
C. An error is thrown at runtime.
D. Compilation fails due to an error on line 3.
E. Compilation fails due to an error on line 8.
F. Compilation fails due to an error on line 9.
Answer (for Objective 2.6):
C is correct. A NoClassDefFoundError is thrown. It’s lame, but you have to watch out for this kind of thing. The invocation should be java -ea BoomBox2 x (both B’s are capitalized). If the invocation was correct, the answer would be A.
A, B, D, E, and F are incorrect based on the above.
7. Given:
2. import java.util.*;
3. public class Olives {
4. public static void main(String[] args) {
5. Set<Integer> s = new TreeSet<Integer>();
6. s.add(23); s.add(42); s.add(new Integer(5));
7. Iterator i = s.iterator();
8. // while(System.out.print(i.next())) { }
9. // for(Integer i2: i) System.out.print(i2);
10. // for(Integer i3: s) System.out.print(i3);
11. // while(i.hasNext()) System.out.print(i.get());
12. // while(i.hasNext()) System.out.print(i.next());
13. } }
If lines 8–12 are uncommented, independently, which are true? (Choose all that apply.)
A. Line 8 will compile.
B. Line 9 will compile.
C. Line 10 will compile.
D. Line 11 will compile.
E. Line 12 will compile.
F. Of those that compile, the output will be 23425
G. Of those that compile, the output will be 52342
Answer (for Objective 6.3):
C, E, and G are correct. Line 10 is a legal for-each loop. Line 12 uses legal syntax to iterate over the Set. Because this is a TreeSet, the output will be sorted.
A, B, D, and F are incorrect based on the above.
8. Given the proper import statements and:
23. try {
24. File file = new File("myFile.txt");
25. PrintWriter pw = new PrintWriter(file);
26. pw.println("line 1");
27. pw.close();
28. PrintWriter pw2 = new PrintWriter("myFile.txt");
29. pw2.println("line 2");
30. pw2.close();
31. } catch (IOException e) { }
What is the result? (Choose all that apply.)
A. No file is created.
B. A file named "myFile.txt" is created.
C. Compilation fails due to an error on line 24.
D. Compilation fails due to an error on line 28.
E. "myFile.txt" contains only one line of data, "line 1"
F. "myFile.txt" contains only one line of data, "line 2"
G. "myFile.txt" contains two lines of data, "line 1" then "line 2"
Answer (for Objective 3.2):
B and F are correct. Both PrintWriter constructors are valid. When the second constructor is called, it truncates the existing file to zero size, then "line 2" is added to the file by the second println().
A, C, D, E, and G are incorrect based on the above.
9. Given this code in a method:
3. String s = "-";
4. boolean b = false;
5. int x = 7, y = 8;
6. if((x < 8) ∧ (b = true)) s += "^";
7. if(!(x > 8) | ++y > 5) s += "|";
8. if(++y > 9 && b == true) s += "&&";
9. if(y % 8 > 1 || y / (x - 7) > 1) s += "%";
10. System.out.println(s);
What is the result?
A. -
B. -|%
C. -^|%
D. -|&&%
E. -^|&&%
F. Compilation fails.
G. An exception is thrown at runtime.
Answer (for Objective 7.6):
D is correct. The first if test fails because both comparisons are true ("b = true" is an assignment, not a test!) and the ∧ is XOR—only one condition can be true. In the second if test, y is incremented because even though the comparison on the left side of the "|" is true, "|" is NOT a short-circuit operator, so the right side will be evaluated. The third if test is true because y has been incremented twice, and b was set to true in the first if test. The fourth if test is true because the left-hand side is true, so the short-circuit operator never tests the right-hand side. If it did, a divide by zero exception would be thrown.
A, B, C, E, F, and G are incorrect based on the above.
10. Given:
3. public class Limits {
4. private int x = 2;
5. protected int y = 3;
6. private static int m1 = 4;
7. protected static int m2 = 5;
8. public static void main(String[] args) {
9. int x = 6; int y = 7;
10. int m1 = 8; int m2 = 9;
11. new Limits().new Secret().go();
12. }
13. class Secret {
14. void go() { System.out.println(x + " " + y + " " + m1 + " " + m2); }
15. } }
What is the result?
A. 2 3 4 5
B. 2 7 4 9
C. 6 3 8 4
D. 6 7 8 9
E. Compilation fails due to multiple errors.
F. Compilation fails due only to an error on line 11.
G. Compilation fails due only to an error on line 14.
Answer (for Objective 1.1):
A is correct. All of the code is legal. The inner class has access to all of the outer class’s variables (even the private ones), except for main()’s local variables. Remember that an inner class must have an instance of the outer class to be tied to, which is why line 11 starts by creating an instance of Limits.
B, C, D, E, F, and G are incorrect based on the above.
11. Note: This question concerns Serialization. As of this writing, the Serialization topic was officially removed from the objectives, BUT we were still getting reports that some testing centers were using versions of the exam that included Serialization questions. If you choose to ignore the Serialization topic, give yourself a free “correct answer” for this question. (FWIW, your authors believe it’s a good topic to understand.)
Given:
3. import java.io.*;
4. class ElectronicDevice { ElectronicDevice() { System.out.print("ed "); }}
5. class Mp3player extends ElectronicDevice implements Serializable {
6. Mp3player() { System.out.print("mp "); }
7. }
8. class MiniPlayer extends Mp3player {
9. MiniPlayer() { System.out.print("mini "); }
10. public static void main(String[] args) {
11. MiniPlayer m = new MiniPlayer();
12. try {
13. FileOutputStream fos = new FileOutputStream("dev.txt");
14. ObjectOutputStream os = new ObjectOutputStream(fos);
15. os.writeObject(m); os.close();
16. FileInputStream fis = new FileInputStream("dev.txt");
17. ObjectInputStream is = new ObjectInputStream(fis);
18. MiniPlayer m2 = (MiniPlayer) is.readObject(); is.close();
19. } catch (Exception x) { System.out.print("x "); }
20. } }
What is the result?
A. ed mp mini
B. ed mp mini ed
C. ed mp mini ed mini
D. ed mp mini ed mp mini
E. Compilation fails.
F. "ed mp mini", followed by an exception.
Answer (for the now defunct Serialization Objective 3.X):
B is correct. It’s okay for Mp3player to implement Serializable even though ElectronicDevice does not. In addition, because Mp3player implements Serializable, its subclass (MiniPlayer) does too. When the MiniPlayer object is deserialized, the only constructor that runs is for the only class that doesn’t implement Serializable or in other words ElectronicDevice.
A, C, D, E, and F are incorrect based on the above.
12. Given:
2. abstract interface Pixie {
3. abstract void sprinkle();
4. static int dust = 3;
5. }
6. abstract class TinkerBell implements Pixie {
7. String fly() { return "flying "; }
8. }
9. public class ForReal extends TinkerBell {
10. public static void main(String[] args) {
11. new ForReal().sprinkle();
12. }
13. public void sprinkle() { System.out.println(fly() + " " + dust); }
14. }
What is the result? (Choose all that apply.)
A. flying 3
B. Compilation fails because TinkerBell doesn’t properly implement Pixie.
C. Compilation fails because ForReal doesn’t properly extend TinkerBell.
D. Compilation fails because Pixie is not a legal interface.
E. Compilation fails because ForReal doesn’t properly implement Pixie.
F. Compilation fails because TinkerBell is not a legal abstract class.
Answer (for Objective 1.2):
A is correct, all of the declaration, implementing, and extending rules are satisfied.
B, C, D, E, and F are incorrect based on the above.
13. Given:
2. public class Errrrr {
3. static String a = null;
4. static String s = "";
5. public static void main(String[] args) {
6. try {
7. a = args[0];
8. System.out.print(a);
9. s += "t1 ";
10. }
11. catch (RuntimeException re) { s += "c1 "; }
12. finally { s += "f1 "; }
13. System.out.println(" " + s);
14. } }
And two command-line invocations:
java Errrrr
java Errrrr x
What is the result?
A. First: f1, then: x t1
B. First: f1, then: x t1 f1
C. First: c1, then: x t1
D. First: c1, then: x t1 f1
E. First: c1 f1, then: x t1
F. First: c1 f1, then: x t1 f1
G. Compilation fails.
Answer (for Objective 2.4):
F is correct. The first invocation throws an exception which is caught, then finally runs. The second invocation throws no exception, but finally still runs.
A, B, C, D, E, and G are incorrect based on the above.
14. Given:
51. String s = "4.5x4.a.3";
52. String[] tokens = s.split("\s");
53. for(String o: tokens)
54. System.out.print(o + " ");
55.
56. System.out.print(" ");
57. tokens = s.split("\..");
58. for(String o: tokens)
59. System.out.print(o + " ");
What is the result?
A. 4 x4
B. 4 x4 .
C. 4 x4 3
D. 4 5x4 a 3 4 x4
E. 4.5x4.a.3 4 x4
F. 4.5x4.a.3 4 x4 .
Answer (for Objective 3.4):
E is correct. The first invocation of split() uses the "s" metacharacter, which splits on whitespace. Since there is no whitespace in String s, the entire string is placed into tokens[0]. The second invocation of split() combines "\." (which means look for "."), with a standalone ".", which is the metacharacter for “find any character.” So the second split() reads “split on a dot followed by any character.” Note that the split() method does not change the String being split.
A, B, C, D, and F are incorrect based on the above.
15. Given:
2. abstract class Tool {
3. int SKU;
4. abstract void getSKU();
5. }
6. public class Hammer {
7. // insert code here
8. }
Which line(s), inserted independently at line 7, will compile? (Choose all that apply.)
A. void getSKU() { ; }
B. private void getSKU() { ; }
C. protected void getSKU() { ; }
D. public void getSKU() { ; }
Answer (for Objective 1.2):
A, B, C, and D are ALL correct. It’s a trick question—you might get something like this on the real exam. It’s easy if you notice that on line 6 the code does NOT say "extends Tool". If line 6 did say "extends Tool", the correct answer would be A, C, and D.
There are no incorrect answers.
16. Given:
3. public class Stubborn implements Runnable {
4. static Thread t1;
5. static int x = 5;
6. public void run() {
7. if(Thread.currentThread().getId() == t1.getId()) shove();
8. else push();
9. }
10. static synchronized void push() { shove(); }
11. static void shove() {
12. synchronized(Stubborn.class) {
13. System.out.print(x-- + " ");
14. try { Thread.sleep(2000); } catch (Exception e) { ; }
15. if(x > 0) push();
16. } }
17. public static void main(String[] args) {
18. t1 = new Thread(new Stubborn());
19. t1.start();
20. new Thread(new Stubborn()).start();
21. } }
Which are true? (Choose all that apply.)
A. Compilation fails.
B. The output is 5 4 3 2 1
C. The output is 5 4 3 2 1 0
D. The program could deadlock.
E. The output could be 5, followed by deadlock.
F. If the sleep() invocation was removed, the chance of deadlock would decrease.
G. As it stands, the program can’t deadlock, but if shove() was changed to synchronized, then the program could deadlock.
Answer (for Objective 4.3):
C is correct. It might look like this code could deadlock, but there is only one lock, so no deadlock can occur.
A, B, D, E, F, and G are incorrect based on the above.
17. Given:
2. class Super {
3. static String os = "";
4. void doStuff() { os += "super "; }
5. }
6. public class PolyTest extends Super {
7. public static void main(String[] args) { new PolyTest().go(); }
8. void go() {
9. Super s = new PolyTest();
10. PolyTest p = (PolyTest)s;
11. p.doStuff();
12. s.doStuff();
13. p.doPoly();
14. s.doPoly();
15. System.out.println(os);
16. }
17. void doStuff() { os += "over "; }
18. void doPoly() { os += "poly "; }
19. }
What is the result?
A. Compilation fails.
B. over over poly poly
C. over super poly poly
D. super super poly poly
E. An exception is thrown at runtime.
Answer (for Objective 5.2):
A is correct. Compilation fails at line 14 because the Super class reference variable doesn’t know about the doPoly() method.
B, C, D, and E are incorrect based on the above.
18. Given two files:
1. package com.wickedlysmart;
2. import com.wickedlysmart2.*;
3. public class Launcher {
4. public static void main(String[] args) {
5. Utils u = new Utils();
6. u.do1();
7. u.do2();
8. u.do3();
9. } }
and the correctly compiled and located:
1. package com.wickedlysmart2;
2. class Utils {
3. void do1() { System.out.print("do1 "); }
4. protected void do2() { System.out.print("do2 "); }
5. public void do3() { System.out.print("do3 "); }
6. }
What is the result for Launcher? (Choose all that apply.)
A. do1 do2 do3
B. "do1 ", followed by an exception
C. Compilation fails due to an error on line 5 of Launcher.
D. Compilation fails due to an error on line 6 of Launcher.
E. Compilation fails due to an error on line 7 of Launcher.
F. Compilation fails due to an error on line 8 of Launcher.
Answer (for Objective 7.1):
C, D, E, and F are correct. class Utils is not public so it CANNOT be accessed from a different package.
A and B are incorrect based on the above.
19. Given:
2. public class Wacky {
3. public static void main(String[] args) {
4. int x = 5;
5. int y = (x < 6) ? 7 : 8;
6. System.out.print(y + " ");
7. boolean b = (x < 6) ? false : true;
8. System.out.println(b + " ");
9. assert(x < 6) : "bob";
10. assert( ((x < 6) ? false : true) ) : "fred";
11. } }
And, if the code compiles, the invocation:
java -ea Wacky
Which will be contained in the output? (Choose all that apply.)
A. 7
B. 8
C. bob
D. fred
E. true
F. false
G. Compilation fails.
Answer (for Objective 7.6):
A, D, and F are correct. The ternary operator assigns the first value when the expression is true, so y == 7, and b == false. The second assert statement has a ternary operator as an expression and since the result is false, fred is added to the AssertionError stack trace.
B, C, E, and G are incorrect based on the above.
20. Given:
3. class MotorVehicle {
4. protected int doStuff(int x) { return x * 2; }
5. }
6. class Bicycle {
7. void go(MotorVehicle m) {
8. System.out.print(m.doStuff(21) + " ");
9. } }
10. public class Beemer extends MotorVehicle {
11. public static void main(String[] args) {
12. System.out.print(new Beemer().doStuff(11) + " ");
13. new Bicycle().go(new Beemer());
14. new Bicycle().go(new MotorVehicle());
15. }
16. int doStuff(int x) { return x * 3; }
17. }
What is the result? (Choose all that apply.)
A. 22 42 42
B. 22 63 63
C. 33 42 42
D. 33 63 42
E. Compilation fails.
F. An exception is thrown at runtime.
Answer (for Objective 5.3):
E is correct. Beemer.doStuff() will not compile because it’s attempting to override using a weaker access modifier.
A, B, C, D, and F are incorrect based on the above.
21. Which are true? (Choose all that apply.)
A. A single JAR file can contain only files from a single package.
B. A JAR file can be used only on the machine on which it was created.
C. When javac is using files within a JAR file, it will unJAR the file during compilation.
D. The Java SDK installation directory tree on a Java developer’s computer usually includes a subdirectory tree named jre/lib/ext.
E. A JAR file is structured so that all the files and directories that you’ve “JARed” will be subdirectory(ies) of the META-INF directory.
F. When javac is invoked with a classpath option, and you need to find files in a JAR file, the name of the JAR file must be included at the end of the path.
Answer (for Objective 7.5):
D and F are correct statements.
A and B are incorrect because JARs can contain many packages, and of course can be used on many machines. C is not true. E is incorrect because your directory structure will be a peer to the META-INF directory.
22. Given the proper import(s), and given:
13. class NameCompare implements Comparator<Stuff> {
14. public int compare(Stuff a, Stuff b) {
15. return b.name.compareTo(a.name);
16. } }
18. class ValueCompare implements Comparator<Stuff> {
19. public int compare(Stuff a, Stuff b) {
20. return (a.value - b.value);
21. } }
Which are true? (Choose all that apply.)
A. This code does not compile.
B. This code allows you to use instances of Stuff as keys in Maps.
C. These two classes properly implement the Comparator interface.
D. NameCompare allows you to sort a collection of Stuff instances alphabetically.
E. ValueCompare allows you to sort a collection of Stuff instances in ascending numeric order.
F. If you changed both occurrences of "compare()" to "compareTo()", the code would compile.
Answer (for Objective 6.3):
C and E are correct. The code is legal and Collections.sort() can use the ValueCompare.compare() method to sort in ascending numeric order.
A is incorrect based on the above. B is incorrect because this code doesn’t show us whether Stuff has overridden equals() and hashCode(), which would allow Stuff to be used successfully for keys. D is incorrect because the NameCompare.compare() method would be used to create sorts in reverse-alphabetical order. F is incorrect based on the above.
23. Given:
3. public class Chopper {
4. String a = "12b";
5. public static void main(String[] args) {
6. System.out.println(new Chopper().chop(args[0]));
7. }
8. int chop(String a) {
9. if(a == null) throw new IllegalArgumentException();
10. return Integer.parseInt(a);
11. } }
And, if the code compiles, the invocation:
java Chopper
What is the result?
A. 12
B. 12b
C. Compilation fails.
D. A NullPointerException is thrown.
E. A NumberFormatException is thrown.
F. An IllegalArgumentException is thrown.
G. An ArrayIndexOutOfBoundsException is thrown.
Answer (for Objective 2.6):
G is correct. Working backwards, if somehow we passed parseInt() the String "12b", it would throw a NumberFormatException. If somehow we passed a null to chop(), we would get an IllegalArgumentException. But before any of that can happen, we attempt to access args[0], which throws an ArrayIndexOutOfBoundsException.
A, B, C, D, E, and F are incorrect based on the above.
24. Which, concerning command-line options, are true? (Choose all that apply.)
A. The -D flag is used in conjunction with a name-value pair.
B. The -D flag can be used with javac to set a system property.
C. The -d flag can be used with java to disable assertions.
D. The -d flag can be used with javac to specify where to place .class files.
E. The -d flag can be used with javac to document the locations of deprecated APIs in source files.
Answer (for Objective 7.2):
A and D are correct.
B is incorrect because -D is used with the java command to set a system property. C is incorrect because -da is used to disable assertions. E is incorrect because the deprecation-related option is -deprecation. Note: You don’t need to memorize all the java and javac command-line options, but -d, -D, and assertion options WILL be on the exam.
25. Given that "it, IT" is the locale code for Italy and that "pt, BR" is the locale code for Brazil, and given:
51. Date d = new Date();
52. DateFormat df = DateFormat.getDateInstance(DateFormat.FULL);
53. Locale[] la = {new Locale("it", "IT"), new Locale("pt", "BR")};
54. for(Locale l: la) {
55. df.setLocale(l);
56. System.out.println(df.format(d));
57. }
Which are true? (Choose all that apply.)
A. An exception is thrown at runtime.
B. Compilation fails due to an error on line 53.
C. Compilation fails due to an error on line 55.
D. Compilation fails due to an error on line 56.
E. The output will contain only today’s date for the Italian locale.
F. The output will contain today’s date for both Italian and Brazilian locales.
Answer (for Objective 3.3):
C is correct. Any instance of DateFormat has an immutable Locale—in other words, there is no setLocale() method. The rest of the code is legal.
A, B, D, E, and F are incorrect based on the above.
26. Given this code in a method:
4. Integer[][] la = {{1,2}, {3,4,5}};
5. Number[] na = la[1];
6. Number[] na2 = (Number[])la[0];
7. Object o = na2;
8. la[1] = (Number[])o;
9. la[0] = (Integer[])o;
What is the result? (Choose all that apply.)
A. Compilation succeeds.
B. Compilation fails due to an error on line 4.
C. Compilation fails due to an error on line 5.
D. Compilation fails due to an error on line 6.
E. Compilation fails due to an error on line 7.
F. Compilation fails due to an error on line 8.
G. Compilation fails due to an error on line 9.
H. Compilation succeeds but an exception is thrown at runtime.
Answer (for Objective 1.3):
F is correct. Integer extends Number, so you can’t refer an Integer[] reference to a Number[] (an Integer can do things a Number can’t.)
A and H are incorrect based on the above. B, C, D, E, and G are incorrect because those lines of code perform legal array manipulations.
27. Given:
3. public class Ice {
4. Long[] stockings = {new Long(3L), new Long(4L), new Long(5L)};
5. static int count = 0;
6. public static void main(String[] args) {
7. new Ice().go();
8. System.out.println(count);
9. }
10. void go() {
11. for(short x = 0; x < 5; x++) {
12. if(x == 2) return;
13. for(long ell: stockings) {
14. count++;
15. if(ell == 4) break;
16. } } } }
What is the result? (Choose all that apply.)
A. 2
B. 4
C. 8
D. 12
E. Compilation fails due to an error on line 13.
F. Compilation fails due to an error on line 16.
Answer (for Objective 2.2):
B is correct. In for loops (any flavor), a return immediately returns execution to the calling method (in this case, main()). A break moves execution to the first statement after the for loop (in this case, the inner for loop).
A, C, D, E, and F are incorrect. Line 13 is a so-called for-each loop that’s using auto-unboxing. Line 16 is ugly but legal. Don’t be surprised to see this kind of thing on the real exam where the number of lines of code is limited by the test engine.
28. Given the proper import statement(s) and:
4. Console c = System.console();
5. char[] pw;
6. if(c == null) return;
7. pw = c.readPassword("%s", "pw: ");
8. System.out.println(c.readLine("%s", "input: "));
Which statements are true? (Choose all that apply.)
A. An exception will be thrown on line 8.
B. The variable pw must be a String, not a char[].
C. No import statements are necessary for the code to compile.
D. If the code compiles and is invoked, line 7 might never run.
E. Without a third argument, the readPassword() method will echo the password the user types.
F. If line 4 was replaced with the following code, the program would still compile: "Console c = new Console();".
Answer (for Objective 3.2):
D is correct. The code is all legal, but it’s possible to invoke a Java program in an environment that doesn’t have a Console object—therefore, the if test on line 6 can sometimes be true. The readPassword() method ALWAYS disables echoing. The Console object is ALWAYS constructed using System.console(), but the Console class is in java.io.
A, B, C, E, and F are incorrect based on the above.
29. Given that:
Exception is the superclass of IOException, and
IOException is the superclass of FileNotFoundException, and
3. import java.io.*;
4. class Physicist {
5. void think() throws IOException { }
6. }
7. public class Feynman extends Physicist {
8. public static void main(String[] args) {
9. new Feynman().think();
10. }
11. // insert method here
12. }
Which of the following methods, inserted independently at line 11, compiles? (Choose all that apply.)
A. void think() throws Exception { }
B. void think() throws FileNotFoundException { }
C. public void think() { }
D. protected void think() throws IOException { }
E. private void think() throws IOException { }
F. void think() { int x = 7/0; }
Answer (for Objective 1.4):
B, C, D, and F are correct. It’s legal for overridden methods to have less restrictive access modifiers, to have fewer or narrower checked exceptions, and to have unchecked exceptions. (Note: Of course, F would throw an exception at runtime.)
A is incorrect because Exception is broader. E is incorrect because private is more restrictive.
30. Given:
4. public class Zingseng extends Thread {
5. public static void main(String[] args) throws Exception {
6. Thread t1 = new Thread(new Zingseng());
7. t1.start();
8. // insert code here
9. for(int i = 0; i < 1000; i++) // Loop #1
10. System.out.print(Thread.currentThread().getName() + " ");
11. }
12. public void run() {
13. for(int i = 0; i < 1000; i++) // Loop #2
14. System.out.print(Thread.currentThread().getName() + " ");
15. } }
Which code, inserted independently at line 8, will make most (or all) of Loop #2’s iterations run before most (or all) of Loop #1’s iterations? (Choose all that apply.)
A. // just a comment
B. t1.join();
C. t1.yield();
D. t1.sleep(1000);
Answer (for Objective 4.2):
B and D are correct. The join() method will tack the main thread’s execution to the end of t1’s execution. The t1.sleep(1000) method will put the main thread to sleep for one second (remember sleep() is static!!!).
A is incorrect because the two threads’ run order will be unpredictable. C is incorrect because yield() might cause a tiny interruption (where 1000 milliseconds would be a HUGE interruption), but it probably wouldn’t significantly change the run order.
31. Given:
2. public class Kant extends Philosopher {
3. // insert code here
5. public static void main(String[] args) {
6. new Kant("Homer");
7. new Kant();
8. }
9. }
10. class Philosopher {
11. Philosopher(String s) { System.out.print(s + " "); }
12. }
Which set(s) of code, inserted independently at line 3, produce the output "Homer Bart "? (Choose all that apply.)
A. Kant() { this("Bart"); }
Kant(String s) { super(s); }
B. Kant() { super("Bart"); }
Kant(String s) { super(s); }
C. Kant() { super(); }
Kant(String s) { super(s); }
D. Kant() { super("Bart"); }
Kant(String s) { this(); }
E. Kant() { super("Bart"); }
Kant(String s) { this("Homer"); }
Answer (for Objective 1.5):
A and B are two correct ways for Kant’s constructors to interact with Philosopher’s constructor.
C will not compile because Kant’s constructors assume Philosopher has a no-arg constructor. D compiles but produces the output "Bart Bart ". E will not compile because the one-arg constructor is attempting to call itself recursively.
32. Given:
2. public class Epoch {
3. static int jurassic = 0;
4. public static void main(String[] args) {
5. assert(doStuff(5));
6. }
7. static boolean doStuff(int x) {
8. jurassic += x;
9. return true;
10. } }
Which are true? (Choose all that apply.)
A. The code compiles using javac -ea Epoch.java
B. The assert statement on line 5 is used appropriately.
C. The code compiles using javac -source 1.3 Epoch.java
D. The code compiles using javac -source 1.4 Epoch.java
E. The code compiles using javac -source 1.6 Epoch.java
F. The code will not compile using any version of the javac compiler.
Answer (for Objective 2.3):
D and E are correct (and C is incorrect) because "assert" was not a keyword until Java 1.4.
A is incorrect because -ea is a java command, not javac. B is incorrect because an assertion should never cause a state change. F is incorrect based on the above.
33. Given
1. public class Kaput {
2. Kaput myK;
3. String degree = "0";
4. public static void main(String[] args) {
5. Kaput k1 = new Kaput();
6. go(k1);
7. System.out.println(k1.degree);
8. }
9. static Kaput go(Kaput k) {
10. final Kaput k1 = new Kaput();
11. k.myK = k1;
12. k.myK.degree = "7";
13. return k.myK;
14. } }
What is the result?
A. 0
B. 7
C. null
D. Compilation fails.
E. An exception is thrown at runtime.
Answer (for Objective 7.3):
A is correct. The Kaput object referred to by k1 has a Kaput object, and that object’s degree variable is updated, but the original Kaput object’s degree variable is not updated.
B, C, D, and E are incorrect based on the above.
34. Given:
3. class Holder {
4. enum Gas { ARGON, HELIUM };
5. }
6. public class Basket extends Holder {
7. public static void main(String[] args) {
8. short s = 7; long 1 = 9L; float f = 4.0f;
9. int i = 3; char c = 'c'; byte b = 5;
10. // insert code here
11. default: System.out.println("howdy");
12. } } }
Which line(s) of code (if any), inserted independently at line 10, will compile? (Choose all that apply.)
A. switch (s) {
B. switch (l) {
C. switch (f) {
D. switch (i) {
E. switch (c) {
F. switch (b) {
G. switch (Gas.ARGON) {
H. The code will not compile due to additional error(s).
Answer (for Objective 2.1):
A, D, E, F, and G are correct. It’s legal to use an enum in a switch.
B and C are incorrect, long and float primitives cannot be used in switch statements.
H is incorrect because the rest of the code is valid.
35. Given
2. class Horse {
3. static String s = "";
4. void beBrisk() { s += "trot "; }
5. }
6. public class Andi extends Horse {
7. void beBrisk() { s += "tolt "; }
8. public static void main(String[] args) {
9. Horse x0 = new Horse();
10. Horse x1 = new Andi(); x1.beBrisk();
11. Andi x2 = (Andi)x1; x2.beBrisk();
12. Andi x3 = (Andi)x0; x3.beBrisk();
13. System.out.println(s);
14. } }
What is the result?
A. tolt tolt tolt
B. trot tolt trot
C. trot tolt tolt
D. Compilation fails.
E. An exception is thrown at runtime.
Answer (for Objective 5.2):
E is correct. On line 12, the code attempts to cast a Horse reference (the superclass) to an Andi reference, causing a ClassCastException.
A, B, C, and D are incorrect based on the above.
36. Given:
3. class Tire {
4. private static int x = 6;
5. public static class Wheel {
6. void go() { System.out.print("roll " + x++); }
7. } }
8. public class Car {
9. public static void main(String[] args) {
10. // insert code here
11. } }
And the three code fragments:
I. new Tire.Wheel().go();
II. Tire t = new Tire(); t.Wheel().go();
III. Tire.Wheel w = new Tire.Wheel(); w.go();
Assuming we insert a single fragment at line 10, which are true? (Choose all that apply.)
A. Once compiled, the output will be "roll 6"
B. Once compiled, the output will be "roll 7"
C. Fragment I, inserted at line 10, will compile.
D. Fragment II, inserted at line 10, will compile.
E. Fragment III, inserted at line 10, will compile.
F. Taken separately, class Tire will not compile on its own.
Answer (for Objective 1.5):
A, C, and E are correct. The weird, static-specific syntax to use so-called “static inner classes” from outside the enclosing class is demonstrated with fragments I and III.
B, D, and F are incorrect based on the above.
37. Given:
3. public class Fortran {
4. static int bump(int i) { return i + 2; }
5. public static void main(String[] args) {
6. for(int x = 0; x < 5; bump(x))
7. System.out.print(x + " ");
8. } }
What is the result?
A. 2 4
B. 0 2 4
C. 2 4 6
D. 0 2 4 6
E. Compilation fails.
F. Some other result occurs.
Answer (for Objective 2.2):
F is correct. In a for loop, the iteration expression can be most any code statement that you want, such as the bump() method call shown on line 6. In this case, the result of the addition is not captured, so x’s value never changes, therefore the for loop runs infinitely. If the iteration expression read "x = bump(x)", then B would be the correct answer.
A, B, C, D, and E are incorrect based on the above.
38. You need the three classes and/or interfaces to work together to produce the output "Kara Charis". Fill in the blanks using the following fragments so the correct is-a and has-a relationships are established to produce this output. Note: You may not need to fill in every empty blank space, but a blank space can hold only one fragment. Also note that not all the fragments will be used, and that fragments CAN be used more than once.
Code to complete:
Fragments:
39. Given:
1. import java.util.*;
2. public class PirateTalk {
3. public static void main(String... arrrrgs) {
4. Properties p = System.getProperties();
5. p.setProperty("pirate", "scurvy");
6. String s = p.getProperty("argProp") + " ";
7. s += p.getProperty("pirate");
8. System.out.println(s);
9. } }
And the command-line invocation:
java PirateTalk -DargProp="dog,"
What is the result?
A. dog, scurvy
B. null scurvy
C. scurvy dog,
D. scurvy null
E. Compilation fails.
F. An exception is thrown at runtime.
G. An “unrecognized option” command-line error is thrown.
Answer (for Objective 7.2):
B is correct. While the declaration of main() could be considered a plank-walking offense, it’s legal. In order to send a system property to the program from the command line, the -D option must come before the name of the class file. As invoked, the JVM will ignore the -D argument, and the call to getProperty() for "argProp" will return a null. If the invocation was:
java -DargProp="dog," PirateTalk then the result would be "dog, scurvy"
A, C, D, E, F, and G are incorrect based on the above.
40. Given:
2. import java.util.*;
3. public class VLA implements Comparator<VLA> {
4. int dishSize;
5. public static void main(String[] args) {
6. VLA[] va = {new VLA(40), new VLA(200), new VLA(60)};
7.
8. for(VLA v: va) System.out.print(v.dishSize + " ");
9. int index = Arrays.binarySearch(va, new VLA(60), va[0]);
10. System.out.print(index + " ");
11. Arrays.sort(va);
12. for(VLA v: va) System.out.print(v.dishSize + " ");
13. index = Arrays.binarySearch(va, new VLA(60), va[0]);
14. System.out.println(index);
15. }
16. public int compare(VLA a, VLA b) {
17. return a.dishSize - b.dishSize;
18. }
19. VLA(int d) { dishSize = d; }
20. }
Which result is most likely?
A. Compilation fails.
B. "40 200 60 2 40 60 200 1"
C. "40 200 60 -2 40 60 200 1"
D. "40 200 60", followed by an exception.
E. "40 200 60 -2", followed by an exception.
Answer (for Objective 6.5):
E is correct. Arrays.sort() assumes that the elements of the array to be sorted implement Comparable unless you provide a Comparator. Note that Arrays .binarySearch() doesn’t throw an exception when passed an unsorted array, it just returns an unpredictable (usually negative) result.
A, B, C, and D are incorrect based on the above.
41. Given:
2. class RainCatcher {
3. static StringBuffer s;
4. public static void main(String[] args) {
5. Integer i = new Integer(42);
6. for(int j = 40; j < i; i--)
7. switch(i) {
8. case 41: s.append("41 ");
9. default: s.append("def ");
10. case 42: s.append("42 ");
11. }
12. System.out.println(s);
13. } }
What is the result?
A. 41 def
B. 41 def 42
C. 42 41 def 42
D. An exception is thrown at runtime.
E. Compilation fails due to an error on line 6.
F. Compilation fails due to an error on line 7.
Answer (for Objective 2.6):
D is correct. A NullPointerException is thrown because no instance of StringBuffer was ever created. If the StringBuffer had been created, autoboxing allows the Integer to be used in the for and the switch, and the switch logic would produce the output in answer C.
A, B, C, E, and F are incorrect based on the above.
42. Given:
2. import java.util.*;
3. class Snack {
4. static List<String> s1 = new ArrayList<String>();
5. }
6. public class Chips extends Snack {
7. public static void main(String[] args) {
8. List c1 = new ArrayList();
9. s1.add("1"); s1.add("2");
10. c1.add("3"); c1.add("4");
11. getStuff(s1, c1);
12. }
13. static void getStuff(List<String> a1, List a2) {
14. for(String s1: a1) System.out.print(s1 + " ");
15. for(String s2: a2) System.out.print(s2 + " ");
16. } }
What is the result? (Choose all that apply.)
A. "1 2 3 4"
B. "1 2", followed by an exception
C. An exception is thrown with no other output.
D. Compilation fails due to an error on line 13.
E. Compilation fails due to an error on line 14.
F. Compilation fails due to an error on line 15.
Answer (for Objective 6.3):
F is correct. When getting elements from a non-generic collection, a cast (from Object) is required. The rest of the code is legal.
A, B, C, D, and E are incorrect based on the above.
43. Given that Calendar.MONTH starts with January == 0, and given:
3. import java.util.*;
4. public class Wise {
5. public static void main(String[] args) {
6. Calendar c = Calendar.getInstance();
7. c.set(1999,11,25);
8. c.roll(Calendar.MONTH, 3);
9. c.add(Calendar.DATE, 10);
10. System.out.println(c.getTime());
11. } }
And, if the program compiles, what date is represented in the output?
A. March 4, 1999
B. April 4, 1999
C. March 4, 2000
D. April 4, 2000
E. Compilation fails.
F. An exception is thrown at runtime.
Answer (for Objective 3.3):
B is correct. It’s important to remember that roll() changes the Calendar field specified WITHOUT incrementing a date’s bigger time chunks. The add() method changes the field’s value AND also increments the bigger time chunks (like adding a new day or month), when appropriate. Note that Calendar instances are created using a factory method.
A, C, D, E, and F are incorrect based on the above.
44. Given the following two files containing Light.java and Dark.java:
2. package ec.ram;
3. public class Light{}
4. class Burn{}
2. package ec.ram;
3. public class Dark{}
4. class Melt{}
And if those files are located in the following directory structure:
$ROOT
|-- Light.java
|-- Dark.java
|-- checker
|-- dira
|-- dirb
And the following commands are executed, in order, from the ROOT directory:
javac Light.java -cp checker/dira -d checker/dirb
javac Dark.java -cp checker/dirb -d checker/dira
jar -cf checker/dira/a.jar checker
A new JAR file is created after executing the above commands. Which of the following files will exist inside that JAR file? (Choose all that apply.)
A. [JAR]/dira/ec/ram/Melt.class
B. [JAR]/checker/dirb/ec/ram/Burn.class
C. [JAR]/dirb/ec/ram/Melt.class
D. [JAR]/checker/dira/ec/ram/Burn.class
E. [JAR]/dira/a.jar
F. [JAR]/checker/dira/a.jar
Answer (for Objective 7.5):
B is correct. When using the jar command with -cf switches, the given source directory will be copied to the JAR file together with its subdirectories and files.
D is incorrect because the -d switch is used to specify the destination directory, so there will be no impact on the classpath directory during compilation or JAR file creation. F is incorrect because there was NO such JAR file before the creation of the new JAR file. A, C, and E are incorrect based on the above.
45. Given:
42. String s1 = " ";
43. StringBuffer s2 = new StringBuffer(" ");
44. StringBuilder s3 = new StringBuilder(" ");
45. for(int i = 0; i < 1000; i++) // Loop #1
46. s1 = s1.concat("a");
47. for(int i = 0; i < 1000; i++) // Loop #2
48. s2.append("a");
49. for(int i = 0; i < 1000; i++) // Loop #3
50. s3.append("a");
Which statements will typically be true? (Choose all that apply.)
A. Compilation fails.
B. Loop #3 will tend to execute faster than Loop #2.
C. Loop #1 will tend to use less memory than the other two loops.
D. Loop #1 will tend to use more memory than the other two loops.
E. All three loops will tend to use about the same amount of memory.
F. In order for this code to compile, the java.util package is required.
G. If multiple threads need to use an object, the s2 object should be safer than the s3 object.
Answer (for Objective 3.1):
B, D, and G are correct. StringBuffer object’s methods are synchronized, which makes them better for multiple threads, and typically a little slower. Because String objects are not mutable, Loop #1 is likely to create about 1000 different String objects in memory.
A, C, E, and F are incorrect based on the above, and because all three classes live in java.lang.
46. Given:
2. public class Payroll {
3. int salary;
4. int getSalary() { return salary; }
5. void setSalary(int s) {
6. assert(s > 30000);
7. salary = s;
8. } }
Which are true? (Choose all that apply.)
A. Compilation fails.
B. The class is well encapsulated as it stands.
C. Removing line 6 would weaken the class’s degree of cohesion.
D. Removing line 6 would weaken the class’s degree of encapsulation.
E. If the salary variable was private, the class would be well encapsulated.
F. Removing line 6 would make the class’s use of assertions more appropriate.
Answer (for Objectives 5.1 and 2.3):
E and F are correct. F is correct because line 6 currently uses the assert mechanism to validate a non-private method’s argument, which is not considered appropriate.
A is incorrect because the code is legal. B is incorrect because salary is not private. C and D are incorrect because the assert mechanism is mainly independent of the OO concepts of cohesion and encapsulation.
47. Given:
1. class GardenTool {
2. static String s = "";
3. String name = "Tool ";
4. GardenTool(String arg) { this(); s += name; }
5. GardenTool() { s += "gt "; }
6. }
7. public class Rake extends GardenTool {
8. { name = "Rake "; }
9. Rake(String arg) { s += name; }
10. public static void main(String[] args) {
11. new GardenTool("hey ");
12. new Rake("hi ");
13. System.out.println(s);
14. }
15. { name = "myRake "; }
16. }
What is the result?
A. Tool Rake
B. Tool myRake
C. gt Tool Rake
D. gt Tool myRake
E. gt Tool gt Rake
F. gt Tool gt myRake
G. gt Tool gt Tool myRake
H. Compilation fails.
Answer (for Objective 5.4):
F is correct. The Rake class has two instance initialization blocks, they run in the order they are encountered in the class, and they run when a new instance is created. Now for the constructors; GardenTool’s 1-arg constructor calls it’s no-arg constructor with the "this();" invocation. Finally, when the Rake is created, there is a call to GardenTool’s no-arg constructor because the compiler added a call to super().
A, B, C, D, E, G, and H are incorrect based on the above.
48. Given:
3. public class Race {
4. public static void main(String[] args) {
5. Horse h = new Horse();
6. Thread t1 = new Thread(h, "Andi");
7. Thread t2 = new Thread(h, "Eyra");
8. new Race().go(t2);
9. t1.start();
0. t2.start();
11. }
12. void go(Thread t) { t.start(); }
13. }
14. class Horse implements Runnable {
15. public void run() {
16. System.out.print(Thread.currentThread().getName() + " ");
17. } }
What is the result? (Choose all that apply.)
A. Compilation fails.
B. No output is produced.
C. The output could be: "Andi Eyra"
D. The output could be: "Eyra Andi Eyra"
E. The output could be: "Eyra", followed by an exception.
F. The output could be: "Eyra Andi", followed by an exception.
Answer (for Objective 4.1):
E and F are correct. Line 10 will throw an exception because you can’t start the same thread (in this case, t2) more than once.
A, B, C, and D are incorrect based on the above.
49. Given the proper import statement(s) and given:
4. Map<String, String> h = new Hashtable<String, String>();
5. String[] k = {"1", "2", "3", null};
6. String[] v = {"a", "b", null, "d"};
7.
8. for(int i=0; i<4; i++) {
9. h.put(k[i], v[i]);
10. System.out.print(h.get(k[i]) + " ");
11. }
12. System.out.print(h.size() + " " + h.values() + "
");
What result is most likely?
A. Compilation fails.
B. "a b d 3 [b, d, a]"
C. "a b null d 3 [b, d, a]"
D. "a b null d 4 [b, d, null, a]"
E. "a b", followed by an exception.
F. "a b null", followed by an exception.
Answer (for Objective 6.1):
E is correct. A Hashtable does NOT allow any null keys OR null values.
A, B, C, D, and F are incorrect based on the above.
50. Given:
3. public class Fiji {
4. static Fiji base;
5. Fiji f;
6. public static void main(String[] args) {
7. new Fiji().go();
8. // do more stuff
9. }
10. void go() {
11. Fiji f1 = new Fiji();
12. base = f1;
13. Fiji f2 = new Fiji();
14. f1.f = f2;
15. Fiji f3 = f1.f;
16. f2.f = f1;
17. base = null; f1 = null; f2 = null;
18. // do stuff
19. } }
Which are true? (Choose all that apply.)
A. At line 8, one object is eligible for garbage collection.
B. At line 8, two objects are eligible for garbage collection.
C. At line 8, three objects are eligible for garbage collection.
D. At line 18, 0 objects are eligible for garbage collection.
E. At line 18, two objects are eligible for garbage collection.
F. At line 18, three objects are eligible for garbage collection.
Answer (for Objective 7.4):
C and D are correct. A total of three Fiji objects are created. At line 18, the anonymous (main()’s), Fiji can still be accessed via "this", and the other two Fiji objects can be accessed via f3 (f3 and f3.f). At line 8, none of the three Fiji objects are accessible.
A, B, E, and F are incorrect based on the above.
51. Your company makes compute-intensive, 3D rendering software for the movie industry. Your chief scientist has just discovered a new algorithm for several key methods in a commonly used utility class. The new algorithm will decrease processing time by 15 percent, without having to change any method signatures. After you change these key methods, and in the course of rigorous system testing, you discover that the changes have introduced no new bugs into the software.
In terms of your software’s overall design, which are probably true? (Choose all that apply.)
A. Your software is well encapsulated.
B. Your software demonstrated low cohesion.
C. Your software demonstrated high cohesion.
D. Your software demonstrated loose coupling.
E. Your software demonstrated tight coupling.
Answer (for Objective 5.1):
A and D are correct. This kind of question can be subjective, so focus on words like “probably.” A is correct. A hallmark of well-encapsulated code is that methods can be re-implemented without causing side effects. D is correct. A hallmark of loose coupling is when one class can change without adversely affecting the workings of classes that interact with it.
B and C are incorrect because it’s not possible to determine the degree of cohesion based on the facts in the scenario. E is incorrect based on the above.
52. Which are true about the classes and interfaces in java.util? (Choose all that apply.)
A. LinkedHashSet is-a Collection
B. Vector is-a List
C. LinkedList is-a Queue
D. LinkedHashMap is-a Collection
E. TreeMap is-a SortedMap
F. Queue is-a Collection
G. Hashtable is-a Set
Answer (for Objective 5.5):
A, B, C, E, and F are correct statements about these classes and interfaces.
D is incorrect. Remember that, in general, Map interfaces and classes do NOT have the Collection interface in their hierarchy. G is incorrect because Hashtable is-a type of Map.
53. Given that File.createNewFile() throws IOException, and that FileNotFoundException extends IOException, use the following fragments to fill in the blanks so that the code compiles. You must use all the fragments, and each fragment can be used only once. Note: As in the real exam, some drag-and-drop style questions might have several correct answers. You will receive full credit for ANY one of the correct answers.
Fragments:
54. Given:
2. class Grandfather {
3. static String name = "gf ";
4. String doStuff() { return "grandf "; }
5. }
6. class Father extends Grandfather {
7. static String name = "fa ";
8. String doStuff() { return "father "; }
9. }
10. public class Child extends Father {
11. static String name = "ch ";
12. String doStuff() { return "child "; }
13. public static void main(String[] args) {
14. Father f = new Father();
15. System.out.print(((Grandfather)f).name
+ ((Grandfather)f).doStuff()) ;
16. Child c = new Child();
17. System.out.println(((Grandfather)c).name
+ ((Grandfather)c).doStuff() + ((Father)c).doStuff());
18. } }