the difference of "==" and "equals“ in Java

Question

Possible Duplicate:
Why are these == but not equals()?

I know in Java, "==" is used to compared reference not values while "equals" to is used to compare values.

Then if

int a=100;
int b=100;
boolean c=(a==b);

Then c will be false? But I remember in my previous project, it seems to be true....

The most common mistake is to use == for Strings, which is not correct because String is not a primitive type. (All datatypes that by default have boldtext in Eclipse is primitive) — Simon Forsberg, Sep 20 '12 at 20:29
@Simon André Forsberg I see. So Strings and other kind of classes are not primitive. Types like int are primitive:> — Hao Shen, Sep 20 '12 at 20:32
int, double, float, boolean... and more are primitive. Primitive types are not classes. See the answer by Jake King for more information on which data types are primitive. — Simon Forsberg, Sep 20 '12 at 20:34

Nathan Hughes · Accepted Answer · 2012-09-20T20:35:41.660

8

c is true, because you're comparing primitives, not references. == compares primitives by value (since the value is all you've got).

edited Sep 20 '12 at 20:35

answered Sep 20 '12 at 20:25

Nathan Hughes

94,330
19
181
276

technically, == compares objects by value too. it just so happens that an object's value is memory location (ie. reference). Hence why java is also always pass by value (and never pass by reference). – Matt Sep 21 '12 at 16:39
@Matt: agreed, the references are passed by value. – Nathan Hughes Sep 21 '12 at 16:54

score 3 · Answer 2 · answered Sep 20 '12 at 20:27

3

Using == works on all primitive data types to compare values, since primitives do not contain references. Objects contain object references instead, so using == compares those instead.

The int value of 100 does equal 100, so c will be true.

answered Sep 20 '12 at 20:27

Alexis King

43,109
15
131
205

+1 for the link reference explaining primitive data types! – Simon Forsberg Sep 20 '12 at 20:30

score 1 · Answer 3 · answered Sep 20 '12 at 20:26

1

c will be true because a and b are primitives and their values are same.

answered Sep 20 '12 at 20:26

kosa

65,990
13
130
167

score 1 · Answer 4 · answered Sep 20 '12 at 20:26

1

Integers are value types. So in this case it just compares the values, so c will be true.

answered Sep 20 '12 at 20:26

Forte L.

2,772
16
25

the difference of "==" and "equals“ in Java

4 Answers4