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org.scopemvc.util
Class WeakSet.WeakEntry  view WeakSet.WeakEntry download WeakSet.WeakEntry.java

java.lang.Object
  extended byjava.lang.ref.Reference
      extended byjava.lang.ref.WeakReference
          extended byorg.scopemvc.util.WeakSet.WeakEntry
Enclosing class:
WeakSet

static class WeakSet.WeakEntry
extends java.lang.ref.WeakReference

Wraps an entry with a weak reference.


Field Summary
private  int hashCode
           
 
Fields inherited from class java.lang.ref.Reference
 
Constructor Summary
private WeakSet.WeakEntry(java.lang.Object entry)
           
private WeakSet.WeakEntry(java.lang.Object entry, java.lang.ref.ReferenceQueue referenceQueue)
           
 
Method Summary
(package private) static WeakSet.WeakEntry create(java.lang.Object entry)
           
(package private) static WeakSet.WeakEntry create(java.lang.Object entry, java.lang.ref.ReferenceQueue referenceQueue)
           
 boolean equals(java.lang.Object o)
          Determine whether this Object is semantically equal to another Object.
 int hashCode()
          Get a value that represents this Object, as uniquely as possible within the confines of an int.
 
Methods inherited from class java.lang.ref.Reference
clear, enqueue, get, isEnqueued
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

hashCode

private final int hashCode
Constructor Detail

WeakSet.WeakEntry

private WeakSet.WeakEntry(java.lang.Object entry)

WeakSet.WeakEntry

private WeakSet.WeakEntry(java.lang.Object entry,
                          java.lang.ref.ReferenceQueue referenceQueue)
Method Detail

create

static WeakSet.WeakEntry create(java.lang.Object entry)

create

static WeakSet.WeakEntry create(java.lang.Object entry,
                                java.lang.ref.ReferenceQueue referenceQueue)

hashCode

public int hashCode()
Description copied from class: java.lang.Object
Get a value that represents this Object, as uniquely as possible within the confines of an int.

There are some requirements on this method which subclasses must follow:

  • Semantic equality implies identical hashcodes. In other words, if a.equals(b) is true, then a.hashCode() == b.hashCode() must be as well. However, the reverse is not necessarily true, and two objects may have the same hashcode without being equal.
  • It must be consistent. Whichever value o.hashCode() returns on the first invocation must be the value returned on all later invocations as long as the object exists. Notice, however, that the result of hashCode may change between separate executions of a Virtual Machine, because it is not invoked on the same object.

Notice that since hashCode is used in java.util.Hashtable and other hashing classes, a poor implementation will degrade the performance of hashing (so don't blindly implement it as returning a constant!). Also, if calculating the hash is time-consuming, a class may consider caching the results.

The default implementation returns System.identityHashCode(this)


equals

public boolean equals(java.lang.Object o)
Description copied from class: java.lang.Object
Determine whether this Object is semantically equal to another Object.

There are some fairly strict requirements on this method which subclasses must follow:

  • It must be transitive. If a.equals(b) and b.equals(c), then a.equals(c) must be true as well.
  • It must be symmetric. a.equals(b) and b.equals(a) must have the same value.
  • It must be reflexive. a.equals(a) must always be true.
  • It must be consistent. Whichever value a.equals(b) returns on the first invocation must be the value returned on all later invocations.
  • a.equals(null) must be false.
  • It must be consistent with hashCode(). That is, a.equals(b) must imply a.hashCode() == b.hashCode(). The reverse is not true; two objects that are not equal may have the same hashcode, but that has the potential to harm hashing performance.

This is typically overridden to throw a java.lang.ClassCastException if the argument is not comparable to the class performing the comparison, but that is not a requirement. It is legal for a.equals(b) to be true even though a.getClass() != b.getClass(). Also, it is typical to never cause a java.lang.NullPointerException.

In general, the Collections API (java.util) use the equals method rather than the == operator to compare objects. However, java.util.IdentityHashMap is an exception to this rule, for its own good reasons.

The default implementation returns this == o.