How != and == operators work on Integers in Java? [duplicate]

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Integers are cached for values between -128 and 127 so Integer i = 127 will always return the same reference. Integer j = 128 will not necessarily do so. You will then need to use equals to test for equality of the underlying int.

This is part of the Java Language Specification:

If the value p being boxed is true, false, a byte, or a char in the range \u0000 to \u007f, or an int or short number between -128 and 127 (inclusive), then let r1 and r2 be the results of any two boxing conversions of p. It is always the case that r1 == r2.

But 2 calls to Integer j = 128 might return the same reference (not guaranteed):

Less memory-limited implementations might, for example, cache all char and short values, as well as int and long values in the range of -32K to +32K.

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