This chapter includes 39 problems that involve strings, numbers, and mathematical operations. We will start by looking at a bunch of classical problems for strings such as counting duplicates, reversing a string, and removing white spaces. Then, we will look at problems dedicated to numbers and mathematical operations such as summing two large numbers and operation overflow, comparing two unsigned numbers, and computing the floor of a division and modulus. Each problem is passed through several solutions, including Java 8's functional style. Moreover, we will be covering problems that concern JDK 9, 10, 11, and 12.

By the end of this chapter, you will know how to use a bunch of techniques so that you can manipulate strings and apply, adapt, and adjust them to many other problems. You will also know how to solve mathematical corner cases that may lead to weird and unpredictable results.