EXPRESSIONS

Shift Operators

15.18

say the operation overflows; the result is then an infinity of appropriate sign. If

the magnitude is too small to represent, we say the operation underflows; the

result is then a zero of appropriate sign. Otherwise, the sum is rounded to the

nearest representable value using IEEE 754 round to nearest mode. The Java

language requires support of gradual underflow as defined by IEEE 754

( 4.2.4).

The binary

 operator performs subtraction when applied to two operands of

numeric type producing the difference of its operands; the left hand operand is the

minuend and the right hand operand is the subtrahend. For both integer and float 

ing point subtraction, it is always the case that

a b

 produces the same result as

a+( b)

. Note that, for integer values, subtraction from zero is the same as nega 

tion. However, for floating point operands, subtraction from zero is

not

 the same

as negation, because if

x

 is

+0.0

, then

0.0 x

 equals

+0.0

, but

 x

 equals

 0.0

.

Despite the fact that overflow, underflow, or loss of information may occur,

evaluation of a numeric additive operator never throws a run time exception.

15.18   Shift Operators

What, I say, is to become of those wretches?

. . . What more can you say to them than  shift for yourselves? 

Thomas Paine,

 The American Crisis

 (1780)

The

shift operators

 include left shift

<<

, signed right shift

>>

, and unsigned right

shift

>>>

; they are syntactically left associative (they group left to right). The left 

hand operand of a shift operator is the value to be shifted; the right hand operand

specifies the shift distance.

ShiftExpression:

AdditiveExpression

ShiftExpression

 <<

AdditiveExpression

ShiftExpression

 >>

AdditiveExpression

ShiftExpression

 >>>

AdditiveExpression

The type of each of the operands of a shift operator must be a primitive inte 

gral type, or a compile time error occurs. Binary numeric promotion ( 5.6.2) is

not

 performed on the operands; rather, unary numeric promotion ( 5.6.1) is per 

formed on each operand separately. The type of the shift expression is the pro 

moted type of the left hand operand.

If the promoted type of the left hand operand is

int

, only the five lowest 

order bits of the right hand operand are used as the shift distance. It is as if the

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