15.14

Unary Operators

EXPRESSIONS

variable and the difference is stored back into the variable. Before the subtraction,

binary numeric promotion ( 5.6.2) is performed on the value

1

 and the value of

the variable. If necessary, the difference is narrowed by a narrowing primitive con 

version ( 5.1.3) to the type of the variable before it is stored. The value of the

postfix decrement expression is the value of the variable

before

the new value is

stored.

A variable that is declared

final

 cannot be decremented, because when an

access of a

final

 variable is used as an expression, the result is a value, not a

variable. Thus, it cannot be used as the operand of a postfix decrement operator.

15.14   Unary Operators

The

unary operators

 include

+

,

,

++

,

,

~

,

!

, and cast operators. Expressions

with unary operators group right to left, so that

 ~x

 means the same as

 (~x)

.

UnaryExpression

:

PreIncrementExpression

PreDecrementExpression

+

UnaryExpression

UnaryExpression

UnaryExpressionNotPlusMinus

PreIncrementExpression

:

++

UnaryExpression

PreDecrementExpression

:

UnaryExpression

UnaryExpressionNotPlusMinus

:

PostfixExpression

~

UnaryExpression

!

UnaryExpression

CastExpression

The following productions from  15.15 are repeated here for convenience:

CastExpression:

(

PrimitiveType

 )

UnaryExpression

(

ReferenceType

 )

UnaryExpressionNotPlusMinus

This portion of the Java grammar contains some tricks to avoid two potential

syntactic ambiguities.

The first potential ambiguity would arise in expressions such as

(p)+q

, which

looks, to a C or C++ programmer, as though it could be either be a cast to type

p

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