THE PACKAGE JAVA.LANG

java.lang.Object

20.1

 @ 

, and the unsigned hexadecimal representation of the hashcode of the object.

In other words, this method returns a string equal to the value of:

getClass().getName() +  @  + Integer.toHexString(hashCode())

Overridden by

Class

 ( 20.3),

Boolean

 ( 20.4),

Character

 ( 20.5),

Inte 

ger

 ( 20.7),

Long

 ( 20.8),

Float

 ( 20.9),

Double

 ( 20.10),

String

 ( 20.12),

StringBuffer

 ( 20.13),

Thread

 ( 20.20),

ThreadGroup

 ( 20.21),

Throwable

( 20.22.4), and

Bitset

 ( 21.2).

20.1.3

public boolean equals(Object obj)

This method indicates whether some other object is  equal to  this one.

The general contract of

equals

 is that it implements an equivalence relation:

It is

reflexive

: for any reference value

x

,

x.equals(x)

 should return

true

.

It is

symmetric

: for any reference values

x

 and

y

,

x.equals(y)

 should return

true

 if and only if

y.equals(x)

 returns

true

.

It is

transitive

: for any reference values

x

,

y

, and

z

, if

x.equals(y)

 returns

true

 and

y.equals(z)

 returns

true

, then

x.equals(z)

 should return

true

.

It is

consistent

: for any reference values

x

 and

y

, multiple invocations of

x.equals(y)

 consistently return

true

 or consistently return

false

, provided

no information used by

x

 and

y

 in

equals

 comparisons is modified.

For any non null reference value

x

,

x.equals(null)

 should return

false

.

The

equals

 method defined by class

Object

 implements the most discrimi 

nating possible equivalence relation on objects; that is, for any reference values

x

and

y

,

((Object)x).equals(y)

 returns

true

 if and only if

x

 and

y

 refer to the

same object.

Overridden by

Boolean

 ( 20.4),

Character

 ( 20.5),

Integer

 ( 20.7),

Long

( 20.8),

Float

 ( 20.9),

Double

 ( 20.10),

String

 ( 20.12), and

Bitset

 ( 21.2).

20.1.4

public int hashCode()

This method is supported principally for the benefit of hash tables such as those

provided by the Java library class

java.util.Hashtable

 ( 21.5).

The general contract of

hashCode

 is as follows:

Whenever it is invoked on the same object more than once during an execu 

tion of a Java application,

hashCode

 must consistently return the same

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