EXPRESSIONS

Logical Complement Operator

!

15.14.6

15.14.4   Unary Minus Operator

The type of the operand expression of the unary

 operator must be a primitive

numeric type, or a compile time error occurs. Unary numeric promotion ( 5.6.1)

is performed on the operand. The type of the unary minus expression is the pro 

moted type of the operand.

At run time, the value of the unary plus expression is the arithmetic negation

of the promoted value of the operand.

For integer values, negation is the same as subtraction from zero. Java uses

two's complement representation for integers, and the range of two's complement

values is not symmetric, so negation of the maximum negative

int

 or

long

 results

in that same maximum negative number. Overflow occurs in this case, but no

exception is thrown. For all integer values

x

,

 x

 equals

(~x)+1

.

For floating point values, negation is not the same as subtraction from zero,

because if

x

 is

+0.0

, then

0.0 x

 equals

+0.0

, but

 x

 equals

 0.0

. Unary minus

merely inverts the sign of a floating point number. Special cases of interest:

If the operand is NaN, the result is NaN (recall that NaN has no sign).

If the operand is an infinity, the result is the infinity of opposite sign.

If the operand is a zero, the result is the zero of opposite sign.

15.14.5   Bitwise Complement Operator

~

The type of the operand expression of the unary

~

 operator must be a primitive

integral type, or a compile time error occurs. Unary numeric promotion ( 5.6.1) is

performed on the operand. The type of the unary bitwise complement expression

is the promoted type of the operand.

At run time, the value of the unary bitwise complement expression is the bit 

wise complement of the promoted value of the operand; note that, in all cases,

~x

equals

( x) 1

.

15.14.6   Logical Complement Operator

!

The type of the operand expression of the unary

!

 operator must be

boolean,

 or a

compile time error occurs. The type of the unary logical complement expression

is

boolean

.

At run time, the value of the unary logical complement expression is

true

 if

the operand value is

false

 and

false

 if the operand value is

true

.

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