The document discusses the bitwise complement operator (~) in Java. It provides an example where a is declared as a byte with a value of 1. The output of ~a is -2. This is explained through a step-by-step process showing the 1's and 2's complement calculations to get from the binary representation of 1 to -2. The document also discusses what would happen if a was a negative number, walking through an example where a is -3 and the output of ~a is 2.