How to Exit a While Loop in Java

How do I exit a while loop in Java?

Use break:

while (true) {
    ....
    if (obj == null) {
        break;
    }
    ....
}

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However, if your code looks exactly like you have specified you can use a normal while loop and change the condition to obj != null:

while (obj != null) {
    ....
}

How to manually exit a while loop (java)

In java String comparison is using equals function "==" might not work

Change

if (bad_input == "x") {
    loop = false;
    return;
}

To

if (bad_input.equals("x")) {
    loop = false;
    return;
}

How to exit a while loop after a certain time?

long startTime = System.currentTimeMillis(); //fetch starting time
while(false||(System.currentTimeMillis()-startTime)<10000)
{
    // do something
}

Thus the statement

(System.currentTimeMillis()-startTime)<10000

Checks if it has been 10 seconds or 10,000 milliseconds since the loop started.

EDIT

As @Julien pointed out, this may fail if your code block inside the while loop takes a lot of time.Thus using ExecutorService would be a good option.

First we would have to implement Runnable

class MyTask implements Runnable
{
    public void run() { 
        // add your code here
    }
}

Then we can use ExecutorService like this,

ExecutorService executor = Executors.newSingleThreadExecutor();
executor.invokeAll(Arrays.asList(new MyTask()), 10, TimeUnit.SECONDS); // Timeout of 10 seconds.
executor.shutdown();

Break while loop inside for loop Java

use the break statement inside the if condition and set a boolean value to a variable.check for the status of that boolean variable just after the for loop ends.if its true then use a break statement to break out of the while loop.

while (!(list.contains("NORTH SOUTH") || list.contains("SOUTH NORTH") || list.contains("WEST EAST") || list.contains("EAST WEST"))) {

    boolean conditionChecker=false;
    for (int i = 0; i < list.size(); i++) {
        for (int k = i + 1; k < list.size(); k++) {
            if (list.get(i).contains("NORTH") && list.get(k).contains("SOUTH") ||
                list.get(i).contains("SOUTH") && list.get(k).contains("NORTH") ||
                list.get(i).contains("WEST") && list.get(k).contains("EAST") ||
                list.get(i).contains("EAST") && list.get(k).contains("WEST")) {
                list.remove(i);
                list.remove(k - 1);
                conditionChecker=true;
                break;

              }
        }
        if(conditionChecker==true){
          break;      
           }
    }

How I stop the While loop after the 3rd invalid attempt?

Like Adam suggested, you'll need a counter, such as:

    int attempt = 0;
    while (hours < 0 || hours > 280) {
        System.out.println("That's not possible, try again!");
        hours = reader.nextInt();
        attempt++;

        // do something if you reach the limit. The >= comparison is 
        // useless before attempt will never go over 4.
        if(attempt == 3){
            // notify the user that something wrong happened
            System.out.println("Your error message here");

            // exit the main function, further code is not processed
            return;
        }
    }

I suggested a message print and returning. For your information, other options can be:

• throw an exception with throw new MaxAttemptReachedException();
• exit the while loop but keep processing the following code with the break; instruction.

How to break a while loop from an if condition inside the while loop?

The break keyword does exactly that. Here is a contrived example:

public static void main(String[] args) {
  int i = 0;
  while (i++ < 10) {
    if (i == 5) break;
  }
  System.out.println(i); //prints 5
}

If you were actually using nested loops, you would be able to use labels.

Exit while loop in java that has switch case?

You need to read input (int choice = input.nextInt();) inside the while loop. Otherwise choice never changes.

int i = 1;
while(i == 1)
{
  int choice = input.nextInt();
  switch(choice)
  {
    case 1:
        System.out.println("Add");
        break;
    case 2:
        System.out.println("Edit");
        break;
    case 3:
        System.out.println("Delete");
        break;
    case 4:
        System.out.println("Search");
        break;
    case 5:
        i = 2;
        break;
    default:
        System.out.println("Invalid Choice .. Try Again.");
  }
}

How to stop while loop without break and exit in java

I would not consider it good code, but for the sake of it (and because most interview questions have weird answers anyway), you could wrap the whole loop in a try-catch and throw an Exception inside the loop.

Or skip the catch block and throw a RuntimeException if the program execution does not need to continue.

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