How do exit two nested loops?

Question

I have been using Java for quite some time, yet my education in loops is somewhat lacking. I know how to create every loop that exists in java and break out of the loops as well. However, I've recently thought about this:

Say I have two nested loops. Could I break out of both loops using just one break statement?

Here is what I have so far.

int points = 0;
int goal = 100;
while (goal <= 100) {
    for (int i = 0; i < goal; i++) {
        if (points > 50) {
           break; // For loop ends, but the while loop does not
        }
        // I know I could put a 'break' statement here and end
        // the while loop, but I want to do it using just
        // one 'break' statement.
        points += i;
    }
}

Is there a way to achieve this?

score 86 · Accepted Answer · edited Jan 05 '19 at 10:03

86

In Java you can use a label to specify which loop to break/continue:

mainLoop:
while (goal <= 100) {
   for (int i = 0; i < goal; i++) {
      if (points > 50) {
         break mainLoop;
      }
      points += i;
   }
}

edited Jan 05 '19 at 10:03

Peter Mortensen

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answered Jul 10 '11 at 00:09

sirbrialliance

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But isn't goto (in this case, pseudo-goto) evil? – zw324 Jul 10 '11 at 00:11
@ZiyaoWei: IMHO `goto` is not "pure-evil". Just use it with caution and only when you really need. – Grzegorz Szpetkowski Jul 10 '11 at 00:13
1

@Grzegorz I do miss the good old days that I could use goto without someone pointing my back;) – zw324 Jul 10 '11 at 00:14
2

@ziyao as long as the code is clear about what happens (the destination is near the goto) it's fine and IMHO cleaner – ratchet freak Jul 10 '11 at 00:14
2

http://xkcd.com/292/, that said, PHP allows you to "break 2;" the Java version is more clean and maintainable IMHO. – sirbrialliance Jul 10 '11 at 00:14
2

Yeah, while I usually prefer encapsuling the inner loop in an extra function because that's usually clearer, using a goto is surely clearer than using an extra boolean variable and setting that. – Voo Jul 10 '11 at 00:40
1

I cant believe I hadn't known this! Thank you so much for the new lesson! – Kyle Aug 10 '15 at 12:17

score 20 · Answer 2 · answered Jul 10 '11 at 00:10

Yes, you can write break with label e.g.:

int points = 0;
int goal = 100;
someLabel:
while (goal <= 100) {
   for (int i = 0; i < goal; i++) {
      if (points > 50) {
         break someLabel;
      }
   points += i;
   }
}
// you are going here after break someLabel;

score 6 · Answer 3 · answered Jul 10 '11 at 00:10

6

There are many ways to skin this cat. Here's one:

int points = 0;
int goal = 100;
boolean finished = false;
while (goal <= 100 && !finished) {
   for (int i = 0; i < goal; i++) {
      if (points > 50) {
         finished = true;
         break;
      }
   points += i;
   }
}

Update: Wow, did not know about breaking with labels. That seems like a better solution.

answered Jul 10 '11 at 00:10

Dan Tao

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Thanks! I wish I could accept all the answers! – fireshadow52 Jul 10 '11 at 00:11
It's cool. Your answer does make sense though. :) – fireshadow52 Jul 10 '11 at 00:15

score 1 · Answer 4 · answered Jul 10 '11 at 00:17

Elementary, dear Watson ...

int points = 0;
int goal = 100;

while (goal <= 100) {
  for (int i = 0; i < goal; i++) {
    if (points > 50) {
      goal++;
      break;
    }
  points += i;
  }
}

or

int points = 0;
int goalim = goal = 100;

while (goal <= goalim) {
  for (int i = 0; i < goal; i++) {
    if (points > 50) {
      goal = goalim + 1;
      break;
    }
  points += i;
  }
}

score 0 · Answer 5 · answered Apr 18 '16 at 17:17

0

You can reset the loop control variables.

int points = 0;
int goal = 100;
while (goal <= 100) {
   for (int i = 0; i < goal; i++) {
      if (points > 50) {
         i = goal = 101;
      }
   points += i;
   }
}

answered Apr 18 '16 at 17:17

Dipto_Das

53
11

score 0 · Answer 6 · edited Jan 05 '19 at 10:04

0

You shouldn't use labels in objective language. You need to rewrite the for/while condition.

So your code should look like:

int points = 0;
int goal = 100;
while (goal <= 100 && points <= 50) {
    for (int i = 0; i < goal && points <= 50; i++) {
        points += i;
    }
}

// Now 'points' is 55

edited Jan 05 '19 at 10:04

Peter Mortensen

30,738
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answered Apr 25 '16 at 09:24

Kacper Obrzut

1
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This does not really answer the question. It is more a comment. – rghome Apr 25 '16 at 09:26
post was updated for a sample code – Kacper Obrzut Apr 25 '16 at 09:33
What do you mean by *"objective language"*? *[Objective-C](http://en.wikipedia.org/wiki/Objective-C)?* – Peter Mortensen Jan 05 '19 at 10:05

How do exit two nested loops?

6 Answers6

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