what Integer.valueOf() returns in java?

Question

Why

Integer.valueOf(1000) == Integer.valueOf(1000)

returns false, while

Integer.valueOf(6) == Integer.valueOf(6)

returns true?

Answer 1

From the documentation:

This method will always cache values in the range -128 to 127, inclusive, and may cache other values outside of this range.

Therefore, Integer.valueOf(6) has only one instance object while Integer.valueOf(1000) creates a new Integer.

Hence Integer.valueOf(6) == Integer.valueOf(6) and Integer.valueOf(1000) != Integer.valueOf(1000)

Answer 2

Because some lower valued Integer objects are cached and reused. So all Integer objects of lower values, like 6, refer to the same Integer instance.