Java while Loop

Introduction

The while loop is one of the fundamental control flow statements in Java that allows repetitive execution of a block of code as long as a specified condition remains true. It is useful for situations where the number of iterations is not known beforehand and the loop needs to continue until a certain condition is met. In this chapter, we will explore the syntax, usage, and examples of the while loop in Java.

Syntax

The basic syntax of the while loop is as follows:

while (condition) {
    // code to be executed
}

Key Points:

  • The condition is evaluated before each iteration.
  • If the condition is true, the code inside the while loop is executed.
  • If the condition is false, the loop terminates, and control passes to the next statement after the loop.

Example

Let’s consider an example where we use the while loop to print numbers from 1 to 5.

Example Code:

public class WhileExample {
    public static void main(String[] args) {
        int count = 1;
        while (count <= 5) {
            System.out.println("Count: " + count);
            count++;
        }
    }
}

Output:

Count: 1
Count: 2
Count: 3
Count: 4
Count: 5

Infinite Loop

A while loop can become an infinite loop if the condition never becomes false. This can happen if the loop control variable is not updated correctly.

Example of Infinite Loop:

public class InfiniteLoopExample {
    public static void main(String[] args) {
        int count = 1;
        while (count <= 5) {
            System.out.println("Count: " + count);
            // Missing count++;
        }
    }
}

In this example, the count variable is never incremented, so the condition count <= 5 remains true indefinitely, causing an infinite loop.

Using break in while Loop

The break statement can be used to exit the loop prematurely, regardless of the condition.

Example with break:

public class BreakInWhileExample {
    public static void main(String[] args) {
        int count = 1;
        while (count <= 5) {
            if (count == 3) {
                break;
            }
            System.out.println("Count: " + count);
            count++;
        }
    }
}

Output:

Count: 1
Count: 2

Using continue in while Loop

The continue statement skips the current iteration of the loop and proceeds with the next iteration.

Example with continue:

public class ContinueInWhileExample {
    public static void main(String[] args) {
        int count = 1;
        while (count <= 5) {
            if (count == 3) {
                count++;
                continue;
            }
            System.out.println("Count: " + count);
            count++;
        }
    }
}

Output:

Count: 1
Count: 2
Count: 4
Count: 5

Diagram: Flow Chart of while Loop

   Start
     |
[initialize]
     |
 [condition]
     |
    / \
  True  False
   /      \
[execute]  End
   |
[update]
   |
  [condition]
   |
  True/False (loop continues)

Conclusion

The while loop is a powerful control flow statement in Java that enables repetitive execution of a block of code based on a condition. It is particularly useful when the number of iterations is not known in advance and needs to be controlled by a condition. By understanding the syntax and usage of the while loop, including how to manage infinite loops and use break and continue statements, you can write more flexible and efficient Java programs.

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