org.erights.e.elib.tables
Class WeakKey

java.lang.Object
  |
  +--org.erights.e.elib.tables.WeakKey

All Implemented Interfaces:

Runnable

class WeakKey

extends Object

implements Runnable

Used to implement a key in a WeakKeyMap implementation by being a key in a FlexMap.

Holds on to the actual key weakly. Is an HONORARY Selfless object, so it compares based on its equals() and hashCode() methods. A WeakKey is also a Runnable, since it stores itself as the reactor to be informed when its key is collected.

WeakKey's implementation of equals and hashCode does not satisfy the contract specified for HONORARY Selfless objects, but that's ok since the WeakKey class is only used in the implementation of WeakKeyMap. It compares the actual keys using identity, which makes sense only for NEAR Selfish objects.

Author:

Mark Miller

Field Summary

private int	myHashCode since the actual key may disappear
private FlexMap	myOptMap the map I'm in, that I need to remove myself from
private WeakPtr	myWeakPtr weakly holds the actual key

Constructor Summary

(package private)

WeakKey(Object key, FlexMap map) The key should be a NEAR Selfish object, but this is not currently enforced.

Method Summary

boolean	equals(Object other) Suppressed: Indicates whether some other object is "equal to" this one.
(package private) Object	getOptActual() If the actual key is still around, return it; else null.
int	hashCode() Suppressed: Returns a hash code value for the object.
void	run() Invoked sometime after the actual key has been gced.
String	toString() Suppressed: Returns a string representation of the object.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

myHashCode

private final int myHashCode

since the actual key may disappear

myWeakPtr

private final WeakPtr myWeakPtr

weakly holds the actual key

myOptMap

private FlexMap myOptMap

the map I'm in, that I need to remove myself from

Constructor Detail

WeakKey

WeakKey(Object key,
        FlexMap map)

The key should be a NEAR Selfish object, but this is not currently enforced.

Method Detail

hashCode

public int hashCode()

Description copied from class: Object

Suppressed: Returns a hash code value for the object. This method is supported for the benefit of hashtables such as those provided by java.util.Hashtable.

The general contract of hashCode is:

• Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
• If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.
• It is not required that if two objects are unequal according to the java.lang.Object#equals(java.lang.Object) method, then calling the hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hashtables.

As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. (This is typically implemented by converting the internal address of the object into an integer, but this implementation technique is not required by the Java^TM programming language.)

Overrides:

hashCode in class Object

Returns:

a hash code value for this object.

See Also:

java.lang.Object#equals(java.lang.Object), java.util.Hashtable

equals

public boolean equals(Object other)

Description copied from class: Object

Suppressed: Indicates whether some other object is "equal to" this one.

The equals method 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 in equals comparisons on the object is modified.
• For any non-null reference value x, x.equals(null) should return false.

The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any reference values x and y, this method returns true if and only if x and y refer to the same object (x==y has the value true).

Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.

Overrides:

equals in class Object

Parameters:

other - the reference object with which to compare.

Returns:

true if this object is the same as the obj argument; false otherwise.

See Also:

Object.hashCode(), java.util.Hashtable

run

public void run()

Invoked sometime after the actual key has been gced.

Specified by:

run in interface Runnable

See Also:

java.lang.Thread#run()

getOptActual

Object getOptActual()

If the actual key is still around, return it; else null.

toString

public String toString()

Description copied from class: Object

Suppressed: Returns a string representation of the object. In general, the toString method returns a string that "textually represents" this object. The result should be a concise but informative representation that is easy for a person to read. It is recommended that all subclasses override this method.

The toString method for class Object returns a string consisting of the name of the class of which the object is an instance, the at-sign character `@', and the unsigned hexadecimal representation of the hash code of the object. In other words, this method returns a string equal to the value of:

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

Overrides:

toString in class Object

Returns:

a string representation of the object.