15.20.2

Boolean Equality Operators

==

and

!=

EXPRESSIONS

The value produced by the

==

 operator is

true

 if the value of the left hand

operand is equal to the value of the right hand operand; otherwise, the result is

false

.

The value produced by the

!=

 operator is

true

 if the value of the left hand

operand is not equal to the value of the right hand operand; otherwise, the

result is

false

.

15.20.2   Boolean Equality Operators

==

and

!=

If the operands of an equality operator are both of type

boolean

, then the opera 

tion is boolean equality. The

boolean

 equality operators are associative.

The result of

==

 is

true

 if the operands are both

true

 or both

false

; other 

wise, the result is

false

.

The result of

!=

 is

false

 if the operands are both

true

 or both

false

; other 

wise, the result is

true

. Thus

!=

 behaves the same as

^

 ( 15.21.2) when applied

to boolean operands.

15.20.3   Reference Equality Operators

==

and

!=

Things are more like they are now than they ever were before.

 Dwight D. Eisenhower

If the operands of an equality operator are both of either reference type or the null

type, then the operation is object equality.

A compile time error occurs if it is impossible to convert the type of either

operand to the type of the other by a casting conversion ( 5.4). The run time val 

ues of the two operands would necessarily be unequal.

At run time, the result of

==

 is

true

 if the operand values are both

null

 or

both refer to the same object or array; otherwise, the result is

false

.

The result of

!=

 is

false

 if the operand values are both

null

 or both refer to

the same object or array; otherwise, the result is

true

.

While

==

 may be used to compare references of type

String

, such an equal 

ity test determines whether or not the two operands refer to the same

String

object. The result is

false

 if the operands are distinct

String

 objects, even if

they contain the same sequence of characters. The contents of two strings

s

 and

t

can be tested for equality by the method invocation

s.equals(t)

 ( 20.12.9). See

also  3.10.5 and  20.12.47.

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