net.spy.util
Class ReferenceSet

java.lang.Object
  java.util.AbstractCollection
      java.util.AbstractSet
          net.spy.util.ReferenceSet

All Implemented Interfaces:

Collection, Set

Direct Known Subclasses:

SoftHashSet

public abstract class ReferenceSet

extends AbstractSet

This class aids in implementing sets of references.

Constructor Summary

ReferenceSet()
Get an instance of ReferenceSet.

ReferenceSet(Collection c)
Get a ReferenceSet with the contents from the given Collection.

ReferenceSet(int n)
Create a ReferenceSet with the given capacity.

Method Summary

boolean	add(Object o) Add an object to the Set.
protected abstract Reference	getReference(Object o) Obtain the desired type of reference to the given object.
Iterator	iterator() Get an iterator.
int	size() Get the current size of the Set.

Methods inherited from class java.util.AbstractSet

equals, hashCode, removeAll

Methods inherited from class java.util.AbstractCollection

addAll, clear, contains, containsAll, isEmpty, remove, retainAll, toArray, toArray, toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Set

addAll, clear, contains, containsAll, isEmpty, remove, retainAll, toArray, toArray

Constructor Detail

ReferenceSet

public ReferenceSet()

Get an instance of ReferenceSet.

ReferenceSet

public ReferenceSet(int n)

Create a ReferenceSet with the given capacity.

Parameters:

n - the initial capacity

ReferenceSet

public ReferenceSet(Collection c)

Get a ReferenceSet with the contents from the given Collection.

Parameters:

c - the collection

Method Detail

add

public boolean add(Object o)

Add an object to the Set.

Parameters:

o - the object

Returns:

true if the object did not already exist

size

public int size()

Get the current size of the Set. This is not an entirely cheap operation, as it walks the entire iterator to make sure all entries are still valid references.

iterator

public Iterator iterator()

Get an iterator. This iterator does not support removing entries due to limitations with HashMap and Iterator that would otherwise require me to duplicate all of HashMap.

getReference

protected abstract Reference getReference(Object o)

Obtain the desired type of reference to the given object.

Unfortunately, java doesn't give me a way to enforce this in the language (i.e. at compile time), but subclasses of ReferenceSet must implement hashCode() and equals() in such a way that they return what the referenced object would return if the object were not a reference. If the reference has disappeared, equals() should return false, and hashCode should return 0.

Parameters:

o - an object

Returns:

a reference to that object