Is it more efficient to put the 'new' in the put method, or use an intermediate variable?

Question

Which of the below ways of adding to a HashMap is more efficient (considering both time and space efficiency)?

Way 1:

Music foo = new Music(Files.getMusic("bar/bold.mp3"));
HashMap.put("rock", foo);

Way 2:

HashMap.put("rock", new Music(Files.getMusic("bar/bold.mp3")));

Identical. Local "temporary" variables are essentially "free" in Java. So the first sequence is preferred because it's easier to read and understand. — Hot Licks, Feb 16 '14 at 21:15

score 1 · Answer 1 · answered Feb 16 '14 at 21:13

1

this is identical. Java objects are passed by reference, you have the exact same number of objects created in both cases.

answered Feb 16 '14 at 21:13

Omry Yadan

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Fix "pass by reference" and I'll remove my downvote. – Sotirios Delimanolis Feb 16 '14 at 21:27
I'll keep my personal opinion to myself, but [it's generally accepted that Java is pass-by-value](http://stackoverflow.com/questions/40480/is-java-pass-by-reference). – Bernhard Barker Feb 16 '14 at 22:24

score 1 · Accepted Answer · answered Feb 16 '14 at 21:13

1

Both are the exact same. When running

new Music(Files.getMusic("bar/bold.mp3"));

You create an object in memory, and return a reference to it. Whether you temporarily store that reference in foo before passing it to the HashMap or not doesn't really make a difference (and even if it would, this would be optimized away).

answered Feb 16 '14 at 21:13

PaF

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Thanks for the explanation :) will be accepted in 10 minutes. – julian Feb 16 '14 at 21:16

Is it more efficient to put the 'new' in the put method, or use an intermediate variable?

2 Answers2