CODEWITHSUNDEEP
javaandroidperformancearraylist
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Reputation: 3916

ArrayList loop performance in ART (Android Runtime Environment)

I have read the performance tips here: http://developer.android.com/training/articles/perf-tips.html#Loops and at the time it looks like 

for(i=0; i <= objectArrayList.size() ; ++i){}

loops are preferred for performance reasons to "for each" or "enhanced" style loops 

for(Object object : objectArrayList){}

Does this still hold true for ART or will that change things? Just wondering.

Upvotes: 4

Views: 215

Answers (2)

Damian Leszczyński - Vash
Damian Leszczyński - Vash

Reputation: 30875

The difference between Dalvik and ART can be really simplified to point that. Dalvik is JIT (Just-in-Time) and ART is AOT (Ahead-of-Time). This refer too the generation of executable code. So all guides that ware valid for dalvik are also valid for ART.

In your case with ArrayList, a better solution in term of memory allocation is the counted loop as you do not create additional instance for iterator. But in term of code maintenance the enhanced for is easier.

The guides that are currently used for Android developers ware wrote few year ago. The are updated but in case you write on device that support android K, this kind of optimization may be classified as premature.

Upvotes: 1

Suresh Atta
Suresh Atta

Reputation: 122026

Not an Android guru :)

Seems a premature Optimization to me. Well you have a valid question though. See

 for(i=0; i <= objectArrayList.size() ; ++i){
       Object o = objectArrayList.get(i);
       /// do stuff
    }

So it traverse each time the list to get that particular element. Where as 

for(Object object : objectArrayList){
  // do stuff
}

Uses iterator and just a bit faster than the normal for. Steps over to next element.

Though I prefer for-each because of readability, since all recent jvm's are super faster ;)

Upvotes: 1

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