Which of these methods is most effective when I cross the list?

Question

List<T> list = new ArrayList<T>();

1 method:

for(int i = list.length - 1; i >= 0; i--) {
  System.out.println(list.get(i));
}

2 method:

for(T t : list) {
  System.out.println(t);
}

3 method:

Iterator<T> it = list.iterator();     
while(it.hasNext()) {
  System.out.println(it.next());
}

Answer 1

Efficiency is unlikely to be significant - of course, it is System.out.printlnmuch more likely to be a bottleneck in your specific example.

The second approach (improved for the loop) is the most readable one. Note that the three approaches do not do the same: the first one will iterate from the end, not from the beginning. Getting the right behavior almost always surpasses a tiny, tiny cue ball faster. The more readable your code is, the more likely it is that you will fix it.

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Answer 2

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Answer 3

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ListIterator<T> it = list.listIterator();
while (it.hasNext()) {
    T t = it.next;
    int index = it.previousIndex();
    System.out.printf("%d => %s%n", index, t);
}

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Answer 4

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}

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Answer 5

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Answer 6

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  System.out.println(list.get(i));
}

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Answer 7

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Answer 8

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Answer 9

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