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What, if any, is the performance difference between the following two loops?
for (Object o: objectArrayList) {
o.DoSomething();
}
and
for (int i=0; i<objectArrayList.size(); i++) {
objectArrayList.get(i).DoSomething();
}
311
The foreach loop is easier to read and write than the for loop. The for loop is used as a general purpose loop. The foreach loop is used for arrays and collections.
The advantage of the for-each loop is that it eliminates the possibility of bugs and makes the code more readable. It is known as the for-each loop because it traverses each element one by one. The drawback of the enhanced for loop is that it cannot traverse the elements in reverse order.
For loop (forward and reverse) The traditional for loop is the fastest, so you should always use that right? Not so fast - performance is not the only thing that matters. Code Readability is usually more important, so default to the style that fits your application.
From Item 46 in Effective Java by Joshua Bloch :
The for-each loop, introduced in release 1.5, gets rid of the clutter and the opportunity for error by hiding the iterator or index variable completely. The resulting idiom applies equally to collections and arrays:
// The preferred idiom for iterating over collections and arrays for (Element e : elements) { doSomething(e); }When you see the colon (:), read it as “in.” Thus, the loop above reads as “for each element e in elements.” Note that there is no performance penalty for using the for-each loop, even for arrays. In fact, it may offer a slight performance advantage over an ordinary for loop in some circumstances, as it computes the limit of the array index only once. While you can do this by hand (Item 45), programmers don’t always do so.
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