Why iteration of a block is prevented in java?

Question

retry: {
       .........
       if(xyz < 5) {
          continue retry;
       }
}

Problem : continue cannot be used outside of a loop

Why iteration of a block is prevented in java?

`goto` should be used with labels. `goto retry`. – Uma Kanth Jun 16 '15 at 06:31 — Uma Kanth, Jun 16 '15 at 06:31

score 2 · Answer 1 · answered Jun 16 '15 at 06:42

It's not supported because noone implemented it, presumably because they thought that, well, loops should be implemented with the loop constructs Java provides.

What you want to do can easily be implemented as a while loop if you invert the condition and use break instead:

while (true) {
  .........
  if(xyz >= 5) {
    break;
  }
}

Or why not write it as a regular loop without break or continue?

do {
  .........
} while (xyz < 5);

Juned Ahsan · Answer 2 · 2015-06-16T06:35:35.503

1

Problem : continue cannot be used outside of a loop

continue is used within a loop i.e. for/while/do-while, if statements are conditional code blocks and not loops.

Learn more about code branching statements here:

https://docs.oracle.com/javase/tutorial/java/nutsandbolts/branch.html

edited Jun 16 '15 at 06:35

answered Jun 16 '15 at 06:31

Juned Ahsan

67,789
12
98
136

`goto` doesn't do anything in Java. – gustafc Jun 16 '15 at 06:35

score 0 · Answer 3 · answered Jun 16 '15 at 06:58

The purpose of continue keyword is to skip rest of the code inside loop to start with the next pass of loop. So, by it's purpose, continue would not fit in the contexts outside the loops.

goto could be other option for you to reset (or restart) the code of execution. However the best way could be move such part into a method and use recursion along with return under specific conditions to achieve the purpose you are talking about.

score 0 · Answer 4 · edited May 23 '17 at 12:30

As others have pointed out, labels in Java label loops, and are used to specify which loop to break or continue.

That said, if you really want to write "spaghetti code" you can misuse break and continue like for instance:

public class SillyGotoExmple {

    public static void main(String args[]) {

        int count, loops;
        final int NUM_LOOPS=2;
        final int MAX_COUNT=10;   

        loops=0;  
        bar: do { 
            count = 0;
            foo: do {
                System.out.println(count);
                if(++count < MAX_COUNT) {
                    continue foo;
                } else if(++loops < NUM_LOOPS) {
                    continue bar;
                } else {
                    break bar;
                } 
            } while (true);
        } while(true);
    }             
}

For some more discussion on goto in Java, see e.g. Is there a goto statement in Java?

Why iteration of a block is prevented in java?

4 Answers4