Using Integer or int in a for each with a collection

Question

I have a quick question that I am a little unclear which is the better practice.

Say I have a collection, c, that holds the numbers 3, 5, and 8.

Collection<Integer> c = new ArrayList<Integer>(); c.add(3); c.add(5); c.add(8);

I understand the idea of a for-each loop, however I am unclear on one part.

Do I write: for(Integer i: c){} or for(int i: c)?

If possible, please comment on speed, efficacy, advantages, and disadvantages or each.

The second can throw a NPE is your collection contains an element that is `null`. — Alexis C., Feb 21 '14 at 22:15
possible duplicate of [Why are there wrapper classes in Java?](http://stackoverflow.com/questions/3579035/why-are-there-wrapper-classes-in-java) — femtoRgon, Feb 21 '14 at 22:15

score 2 · Accepted Answer · answered Feb 21 '14 at 22:14

It depends on what you're doing inside the for-each loop, and whether you'll need to "re-box" an int, or how often you'll need to unbox an Integer. It also depends how or if you want null to be handled -- if you want null to be allowed, you have to use Integer.

Frankly, it's unlikely to make a significant difference either way.

score 1 · Answer 2 · answered Feb 21 '14 at 22:16

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Integer maps an int value as object so an it can be null but an int can't. So an int is a basic type so it uses less memory than the Integer object

answered Feb 21 '14 at 22:16

Athanor

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But you already have a boxed `Integer`, so you're not actually saving or losing memory either way. – Louis Wasserman Feb 21 '14 at 22:17

Steve Kuo · Answer 3 · 2014-03-31T02:37:21.877

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Your collection contains Integers, this it's better to iterate using for (Integer i: c). You'll want to do this to avoid unnecessary unboxing of Integer to int.

edited Mar 31 '14 at 02:37

answered Feb 21 '14 at 22:17

Steve Kuo

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Using Integer or int in a for each with a collection

3 Answers3