Which is better? isEmpty() or size() == 0?

Question

I'm wondering why there's an isEmpty() method in Java's List interface since there's a size() method. And when used as a loop guard, which one is better, list.isEmpty() or list.size == 0?

I seem to recall a duplicate, the implementation of isEmpty() was return size==0; in the oracle implementation. — Captain Giraffe, Aug 19 '14 at 22:28
In terms of performance? Readability? Or in terms of some other criteria? — mostruash, Aug 19 '14 at 22:29
In some implementations, isEmpty is cheaper than size - a linked list, for example. — Blorgbeard, Aug 19 '14 at 22:29
See http://stackoverflow.com/questions/1508975/why-is-list-size0-slower-than-list-isempty-in-java — ROMANIA_engineer, Aug 19 '14 at 22:30
http://pmd.sourceforge.net/pmd-4.3.0/rules/design.html#UseCollectionIsEmpty — Engineer2021, Aug 19 '14 at 22:30
Semantics makes the difference here if ( stuffs.isEmpty() ) conveys a lot more meaning than == 0. — Captain Giraffe, Aug 19 '14 at 22:31

score 0 · Answer 1 · answered Aug 19 '14 at 22:28

0

I'd say they are the same :

 public boolean isEmpty() {
     return size == 0;
 }

 public int size() {
     return size;
 }

answered Aug 19 '14 at 22:28

Eran

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Do you recall the duplicate Q? – Captain Giraffe Aug 19 '14 at 22:29

score 0 · Answer 2 · edited Aug 20 '14 at 00:04

0

Most implementations of List.isEmpty() actually tests for List.size() == 0. That being said the JVM can easily optimize this method and it is best to use List.isEmpty() over List.size() == 0 for clarity purposes.

edited Aug 20 '14 at 00:04

hlt

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answered Aug 19 '14 at 22:29

Smith_61

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Which is better? isEmpty() or size() == 0?

2 Answers2