Java while Loop

In this chapter you will learn:

1. What is Java while loop
2. How to use the basic Java While Loop
3. Note for Java while Loop
4. Example - Java while loop
5. Example - while condition
6. Example - while loopbody

Description

The while loop repeats a statement or block while its controlling condition is true.

Syntax

Here is its general form:

while(condition) { 
   // body of loop 
}

Note

• The condition can be any Boolean expression.
• The body of the loop will be executed as long as the conditional condition is true.
• The curly braces are unnecessary if only a single statement is being repeated.

Example

Here is a while loop that counts down from 10, printing exactly ten lines of "tick":

 
public class Main {
  public static void main(String args[]) {
    int n = 10;//from  w w w  .  j  a v a  2s  . c  om
    while (n > 0) {
      System.out.println("n:" + n);
      n--;
    }
  }
}

When you run this program, you will get the following result:

Example 2

The body of the while loop will not execute if the condition is false. For example, in the following fragment, the call to println() is never executed:

 
public class Main {
  public static void main(String[] argv) {
    int a = 10, b = 20;
    while (a > b) {
      System.out.println("This will not be displayed");
    }/*  w ww.  j a  va2  s  .c o  m*/
    System.out.println("You are here");
  }
}

The output:

Example 3

The body of the while can be empty. For example, consider the following program:

 
public class Main {
  public static void main(String args[]) {
    int i, j;//  w  w  w . java  2  s  . com
    i = 10;
    j = 20;

    // find midpoint between i and j
    while (++i < --j)
      ;
    System.out.println("Midpoint is " + i);
  }
}

The while loop in the code above has no loop body and i and j are calculated in the while loop condition statement. It generates the following output:

Next chapter...

What you will learn in the next chapter:

1. Why do we need Java do while loop
2. Syntax for Java do while loop
3. Example - How to use do-while statement
4. How to create a simple help menu with while loop and switch statement

Java while Loop