A
unary expression returns different results depending on which of
the unary operators is used.
Expression
Character representation
Returns
Unary
-
The arithmetic negation of the operand,
or null if the operand is null.
+
The arithmetic value of the operand (unchanged),
or null if its operand is null.
not
The logical negation of the operand.
Note:
The arithmetic negation of a null operand yields
the result null, whereas the logical negation of a null operand
yields the Boolean result true. This is justified by the common
sense statement: If null means nothing, then “not nothing” should
be something.
