Everything is driven by the
Java Language Specification:
15.21.1 Numerical Equality Operators == and !=
If the operands of an equality operator are both of numeric type, or one is of numeric type and the other is convertible (�5.1.8) to numeric type, binary numeric promotion is performed on the operands (�5.6.2).
So the Integer object is unboxed to an
int and a binary comparison takes place on the two operands. In comparing two entities representing numeric values, the most logical thing (to me) is to compare their values not their arbitrary memory addresses. Unboxing the Integer to an
int is more optimal performance wise, than boxing the
int and then comparing the numerical values of two Integer objects (which would anyway be a binary comparison).