How do I exit a while loop in Java?

问题

What is the best way to exit/terminate a while loop in Java?

For example, my code is currently as follows:

while(true){
    if(obj == null){

        // I need to exit here

    }
}

回答1:

Use break:

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

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) {
    ....
}

回答2:

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

回答3:

break is what you're looking for:

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

alternatively, restructure your loop:

while (obj != null) {
    // do stuff
}

or:

do {
    // do stuff
} while (obj != null);

回答4:

Finding a while...do construct with while(true) in my code would make my eyes bleed. Use a standard while loop instead:

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

And take a look at the link Yacoby provided in his answer, and this one too. Seriously.

The while and do-while Statements

回答5:

You can do multiple condition logical tests within the while() check using the same rules as within any logical check.

while ( obj != null ) {  
    // do stuff  
}

works, as does

while ( value > 5 && value < 10 ) {  
    // do stuff  
}

are valid. The conditionals are checked on each iteration through the loop. As soon as one doesn't match, the while() loop is exited. You can also use break;

while ( value > 5 ) {  
    if ( value > 10 ) { break; }  
    ...  
}

回答6:

Take a look at the Java™ Tutorials by Oracle.

But basically, as dacwe said, use break.

If you can it is often clearer to avoid using break and put the check as a condition of the while loop, or using something like a do while loop. This isn't always possible though.

回答7:

You can use "break", already mentioned in the answers above. If you need to return some values. You can use "return" like the code below:

 while(true){
       if(some condition){
            do something;
            return;}
        else{
            do something;
            return;}
            }

in this case, this while is in under a method which is returning some kind of values.

回答8:

if you write while(true). its means that loop will not stop in any situation for stop this loop you have to use break statement between while block.

package com.java.demo;

/**
 * @author Ankit Sood Apr 20, 2017
 */
public class Demo {

    /**
     * The main method.
     *
     * @param args
     *            the arguments
     */
    public static void main(String[] args) {
        /* Initialize while loop */
        while (true) {
            /*
            * You have to declare some condition to stop while loop 

            * In which situation or condition you want to terminate while loop.
            * conditions like: if(condition){break}, if(var==10){break} etc... 
            */

            /* break keyword is for stop while loop */

            break;
        }
    }
}

来源：https://stackoverflow.com/questions/7951690/how-do-i-exit-a-while-loop-in-java

标签

java

while-loop

exit

break