15.20.1 Numerical Equality Operators == and !=

If the operands of an equality operator are both of primitive numeric type, binary numeric promotion is performed on the operands (§5.6.2). If the promoted type of the operands is int or long, then an integer equality test is performed; if the promoted type is float or double, then a floating-point equality test is performed.

Floating-point equality testing is performed in accordance with the rules of the IEEE 754 standard:

• If either operand is NaN, then the result of == is false but the result of != is true. Indeed, the test x!=x is true if and only if the value of x is NaN. (The methods Float.isNaN (§20.9.19) and Double.isNaN (§20.10.17) may also be used to test whether a value is NaN.)
• Positive zero and negative zero are considered equal. Therefore, -0.0==0.0 is true, for example.
• Otherwise, two distinct floating-point values are considered unequal by the equality operators. In particular, there is one value representing positive infinity and one value representing negative infinity; each compares equal only to itself, and each compares unequal to all other values.

Subject to these considerations for floating-point numbers, the following rules then hold for integer operands or for floating-point operands other than NaN:

• The value produced by the == operator is true if the value of the left-hand operand is equal to the value of the right-hand operand; otherwise, the result is false.
• The value produced by the != operator is true if the value of the left-hand operand is not equal to the value of the right-hand operand; otherwise, the result is false.