Local Variables

A local variable is a variable that’s declared within the body of a method. Then you can use the variable only within that method. Other methods in the class aren’t even aware that the variable exists.

Here’s a program that uses a local variable:

public class HelloApp

{

public static void main(String[] args)

{

String helloMessage;

helloMessage = “Hello, World!”;

System.out.println(helloMessage);

}

}

You don’t specify static on a declaration for a local variable. If you do, the compiler generates an error message and refuses to compile your program.

Unlike class and instance variables, a local variable is fussy about where you position the declaration for it: You must place the declaration before the first statement that actually uses the variable.

You may also declare local variables within blocks of code marked by braces. For example:

if (taxRate > 0)

{

double taxAmount;

taxAmount = subTotal * taxRate;

total = subTotal + total;

}

Local variables are not given initial default values. Thus, you must assign a value before you use a local variable.

One way to initialize a variable is to code an assignment statement following the variable declaration. Assignment statements have this general form:

variable = expression;

Here, the expression can be any Java expression that yields a value of the same type as the variable. For example, here’s a method that declares a local variable named i, and then initializes the variable before using it:

public static void main(String[] args)

{

int i;

i = 0;

System.out.println(“i is “ + i);

}

For more information, see Assignment Statement.

Another way to initialize a variable is to use an initializer, which lets you assign an initial value to a variable at the time you declare the variable. Here’s the general form:

type name = expression;

Here are some examples:

int x = 0;

String lastName = “Lowe”;

double radius = 15.4;

In each case, the variable is declared and initialized in a single statement.

When you declare more than one variable in a single statement, each variable can have its own initializer:

int x = 5, y = 10;

When you declare two class or instance variables in a single statement but use only one initializer, the initializer applies only to the last variable in the list. For example:

static int x, y = 5;

Here, only y is initialized.