Alternative for 'continue' keyword

Question

I was browsing through questions regarding continue keyword to get a better understanding of it and I stumbled upon this line in this answer

These can be maintenance timebombs because there is no immediate link between the "continue"/"break" and the loop it is continuing/breaking other than context;

I have this for loop:

for(Object obj : myArrayList){
  if(myArrayList.contains(someParticularData)){
       continue;
    }
   //do something
}

Now, my question is - Is it okay to use continue in the manner that I have done above or does it have any issues? If yes, what is the alternative approach that I can follow? Any kind of guidance would help. Thank you.

Update: My objective in this particular situation would be to iterate over a Collection ( ArrayList, in this case), and check if that contains some particular data and skip that iteration if it is true. I was pointed out that myArrayList.contains(someParticularData) is a one time operation and that it would be better off to perform that check outside the loop, which is what I was looking for. Also, I learnt that if I can use continue based on some condition if(someConditon), I can very well avoid it by using if(!someCondition).

The usage depends on your logical implementation. One box doesn't fit for all sizes. — RaceBase, Feb 04 '14 at 06:36
Will effect readability and code maintenance if you are nesting loops, otherwise it is ok. — Not a bug, Feb 04 '14 at 06:41
Don't close question as "primarily opinion-based" if you think Question is not suitable for SO flag to migrate to [Programmers Stackexchange](http://programmers.stackexchange.com/questions) — Grijesh Chauhan, Feb 04 '14 at 07:19
_slightly related side note_: the use of continue/break could in some respect be equated with the concept of [Single Function Exit Point](http://c2.com/cgi/wiki?SingleFunctionExitPoint) http://stackoverflow.com/questions/36707/should-a-function-have-only-one-return-statement — zamnuts, Feb 04 '14 at 08:15

score 17 · Accepted Answer · 2014-02-04T06:42:34.883

17

for(Object obj : myArrayList){
    if(someCondition){
       continue;
    }
    //do something 
}

can be replaced with:

for(Object obj : myArrayList){
    if(!someCondition){
       //do something 
    }
}

IMHO, as far as you don't have a lot (like 2-3 continue/break/return), maintenance will be fine.

edited Feb 04 '14 at 06:42

answered Feb 04 '14 at 06:34

Dmitry Bychenko · Answer 2 · 2014-02-04T07:15:16.640

13

This code is of little use

  for(Object obj : myArrayList) {
    // You're checking again and agian the condition that's loop independent
    if(myArrayList.contains(someParticularData)){
      continue;
    }
   //do something
  }

A more effective implementation is (check whether you need the loop at all first)

  if (!myArrayList.contains(someParticularData))
    for(Object obj: myArrayList) {
      //do something
    }

continue is convenient in conditions like that:

  for(Object obj : myArrayList) {
    // Check for each item: do we need to proceed this item
    if (someArrayList.contains(obj))
      continue;

    //do something
  }

edited Feb 04 '14 at 07:15

answered Feb 04 '14 at 06:38

Dmitry Bychenko

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good catch! I missed that – Feb 04 '14 at 06:39
I'm sorry but were you asking me to check if the `for` loop is needed at all? If so, yes, I need to loop through a `Collection` and in case it contains a particular data, I want to skip that iteration. – Anjan Baradwaj Feb 04 '14 at 06:44
1

@AnjanBaradwaj - What Dmitry is trying to say is "ArrayList.contains()" is a one-time operation.. putting it in a for loop doesn't help.. – TheLostMind Feb 04 '14 at 06:46
@Dmitry , I assume that `Contains` in the last snippet was supposed to be lower case? – Dennis Meng Feb 04 '14 at 07:14
@Dennis Meng: Yes, thank you! I haven't switched my mind from C# (where "Contains" capitalized) to Java – Dmitry Bychenko Feb 04 '14 at 07:16

score 1 · Answer 3 · answered Feb 04 '14 at 06:58

Whenever you are looping on some value range, you are processing on each of the value comes between the initial and final one...

For example if you are making addition of odd numbers. it is convenient to use loop which will be incremented by 2 rather than continuing for each odd value,

for (int i = 0; i < 100 ; i=i+2){
   // do addition
}

but if you are modifying your value that is being checked within the loop, than continue or break is good practice to implement.

for example,

boolean flag = false;
// flag will be modified in some iteration of loop, but you don't know which.
for ( int i = 0 ; i < 100 ; i++ ) {
   if ( flag ) {
      continue;
   }
   // flag modified somewhere..
}

Alternative for 'continue' keyword

3 Answers3