Integer and Double difference

Question

Thanks in advance... Please explain why following happens :

Integer i1 = 6;
Integer i2 = 6;

(i1 == i2) will return true.

while

Double d1 = 6.5;
Double d2 = 6.5;

(d1 == d2) will return false.

Why is that? There will be only one object created in both the cases still they behave differently. Using equals method would be better but I was surprised by this behaviour and just wanted to know.

This should provide some insight: http://stackoverflow.com/questions/3131136/integers-caching-in-java — Mike Koch, Jan 22 '14 at 18:12
@user3199285: your question is basically a duplicate of: http://stackoverflow.com/questions/13098143/java-integer-constant-pool — TacticalCoder, Jan 22 '14 at 18:12
See this answer: http://stackoverflow.com/questions/8081827/how-to-compare-two-double-values-in-java — Rick S, Jan 22 '14 at 18:13
Look at the source code of Integer.valueOf and Double.valueOf. — Boann, Jan 22 '14 at 18:14

user1445967 · Accepted Answer · 2014-01-22T18:47:21.853

You are comparing Integer (capital I) objects by reference, which is not the "proper" way to compare objects in java.

References to some integers are cached in order to optimize for performance. This is why comparing certain Integer (capital I) objects by reference seems to work in a few cases in Java.

This is NOT a behavior that the Java developer is expected to rely on or make use of, as it is unreliable, may change, and makes code more difficult to understand.

score 2 · Answer 2 · answered Jan 22 '14 at 18:13

2

The official explanation is here, the last 4 paragraphs in chapter 5.1.7.

answered Jan 22 '14 at 18:13

Dan D.

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Integer and Double difference

2 Answers2