How can I break from a try/catch block without throwing an exception in Java

问题

I need a way to break from the middle of try/catch block without throwing an exception. Something that is similar to the break and continue in for loops. Is this possible?

I have been getting weird throughts about throwing a custom exception (naming it "BreakContinueException") that simple does nothing in its catch handler. I'm sure this is very twisted.

So, any straight forward solution I'm not aware of?

回答1:

The proper way to do it is probably to break down the method by putting the try-catch block in a separate method, and use a return statement:

public void someMethod() {
    try {
        ...
        if (condition)
            return;
        ...
    } catch (SomeException e) {
        ...
    }
}

If the code involves lots of local variables, you may also consider using a break from a labeled block, as suggested by Stephen C:

label: try {
    ...
    if (condition)
        break label;
    ...
} catch (SomeException e) {
    ...
}

回答2:

You can always do it with a break from a loop construct or a labeled break as specified in aioobies answer.

public static void main(String[] args) {
    do {
        try {
            // code..
            if (condition)
                break;
            // more code...
        } catch (Exception e) {

        }
    } while (false);
}

回答3:

Various ways:

return
break or continue when in a loop
break to label when in a labeled statement (see @aioobe's example)
break when in a switch statement.

...

System.exit() ... though that's probably not what you mean.

In my opinion, "break to label" is the most natural (least contorted) way to do this if you just want to get out of a try/catch. But it could be confusing to novice Java programmers who have never encountered that Java construct.

But while labels are obscure, in my opinion wrapping the code in a do ... while (false) so that you can use a break is a worse idea. This will confuse non-novices as well as novices. It is better for novices (and non-novices!) to learn about labeled statements.

By the way, return works in the case where you need to break out of a finally. But you should avoid doing a return in a finally block because the semantics are a bit confusing, and liable to give the reader a headache.

回答4:

There are several ways to do it:

Move the code into a new method and return from it
Wrap the try/catch in a do{}while(false); loop.

回答5:

This is the code I usually do:

 try
 {
    ...........
    throw null;//this line just works like a 'break'
    ...........   
  }
  catch (NullReferenceException)
  { 
  }
  catch (System.Exception ex)
  {
      .........
  }

回答6:

In this sample in catch block i change the value of counter and it will break while block:

class TestBreak {
    public static void main(String[] a) {
        int counter = 0;

        while(counter<5) {
            try {
                counter++;
                int x = counter/0;
            }
            catch(Exception e) {
                counter = 1000;    
            }
        }
    }
}k

回答7:

how about return it will do, if there is no finally

来源：https://stackoverflow.com/questions/6534072/how-can-i-break-from-a-try-catch-block-without-throwing-an-exception-in-java

标签

java

try-catch-finally