4.2. The while Loop

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Chapter 4. Loops

Mayan God Shel, Mexico. Photographer: Philip Coblentz. Courtesy Brand X Pictures.

Objectives

• To use while , do-while , and for loop statements to control the repetition of statements ( § §4.2 “4.4).

• To understand the flow of control in loop statements ( § §4.2 “4.4).

• To use Boolean expressions to control loop statements ( § §4.2 “4.4).

• To know the similarities and differences between three types of loops ( §4.5).

• To write nested loops ( §4.6).

• To implement program control with break and continue ( §4.9).

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4.1. Introduction

Suppose that you need to print a string (e.g., "Welcome to Java!" ) a hundred times. It would be tedious to have to write the following statement a hundred times:

 System.out.println(   "Welcome to Java!"   ); 

Java provides a powerful control structure called a loop that controls how many times an operation or a sequence of operations is performed in succession. Using a loop statement, you simply tell the computer to print a string a hundred times without having to code the print statement a hundred times.

Loops are structures that control repeated executions of a block of statements. The concept of looping is fundamental to programming. Java provides three types of loop statements: while loops, do-while loops, and for loops.