Comparison of 2 Integer values with "=="

1.
{
Integer i1=127;
Integer i2=127;

System.out.println(i1==i2);
}
output:true

2.
{
Integer i1=129;
Integer i2=129;

System.out.println(i1==i2);
}
output:false

Why is the output of "1." and "2." different even if the difference is only in the values.

When comparing objects like the Integer class, you have to you the equals(Object other) to compare their values. '==' will only compare the references of the objects, not their values.

Hunter

You get a difference in output because the operator == behaves differently for Integer/Short objects (created through auto-boxing) initialized with literal values in the range of -128 to +127. This is done to save memory.

The reason is caching of values between -128 and 127 in combination with autoboxing. If you SearchFirst you'll find a few threads with more detailed explanations.

I like this topic about the same problem.

Actually it says in the Java™ Language Specification that at least the range -128..+127 must be cached. It also says it is preferable for larger ranges to be cached. So the behaviour of == for Integer objects might change from JVM to JVM and might be different next year from this year.