Why is == true for some Integer objects? [duplicate]

Answer 1

Here in this case the Integer i and Integer j holding the integer values which are in range of integer, range of an Integer is -128 to 128, and Integer n and Integer m exceeds the range of Integer

Answer 2

Integer objects may be cached for the ones that represent a value close to 0. (The specification for the implementation may tell you some details). This is presumably to save memory (values close to 0 are common, and it would waste a lot of memory to make a new object for every variable with the same value).

== checks whether two things are the same object; you may or may not have the same Integer object for any two given variables with the same value. You are not supposed to check with == because you are not supposed to care whether it is the same object; it is the value of an Integer that matters, not its identity.

Answer 3

The answers about caching are correct. However, if you go...

Integer i = new Integer(10);
Integer j = new Integer(10);

...then you avoid the caching and the results will be what you expected.

Answer 4

In the first case, both the objects i and j are pointing to the same cached object. By default, the range between -128 and 127 are cached as Integer Object. We can increase the range using JVM arguments