Java While Statement Sample


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This is a sample of repeating a process with Java's while statement.

Table of Contents

sample What is the while statement? / Sample while statement
  Exiting the loop(break) / Exit the double loop(label)
  Return to the top of the loop(continue)
How to stop an infinite loop (when using Eclipse)

What is the while statement?

while (conditions){
      Process to be executed
}
  • Repeats the internal process while the condition is true.
  • If the condition is false, the loop process will be terminated.
  • If the first conditional decision is false, the loop will not execute even once.
  • Note that if there is no logic in the process to set the condition to false, it will result in an infinite loop.

Sample while statement

public class Test1 {
	public static void main(String[] args) {
		int i = 0;

		while (i < 5) {
			System.out.println(i); // 0,1,2,3,4
			i++;
		}
	}
}

Line 5 repeats the process while the value is less than 5.
The seventh line adds the value that is the condition.

Exiting the loop(break)

  int i = 0;

  while(true){
    if (i == 3) {
      break;
    }
    System.out.println(i); //0,1,2
    i++;
  }

The break in line 5 exits the while statement.
The third line sets the condition to true. Note that this sample will become an infinite loop without the break in line 5.

Exit the double loop(label)

  int i = 0;
  while1: while (true) {
    while (true) {
      if (i == 3) {
        break while1;
      }
      System.out.println(i); // 0,1,2
      i++;
    }
  }
  System.out.println("end"); // end

It is a double loop with two while's, where while1 is a label.
The break and label in line 5 breaks the outer while statement.

Return to the top of the loop(continue)

  int i = 0;
        
  while(i < 5){
    if (i == 3) {
      i++;
      continue;
    }
    System.out.println(i); //0,1,2,4
    i++;
  }

The continuation of line 6 executes line 3 next.
Note that in this sample, if there is no addition in line 5, it will become an infinite loop.

How to stop an infinite loop (when using Eclipse)

If you encounter an infinite loop when using Eclipse, press the red square icon in the "Console" tab. (Eclipse 4.8)

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