Top Description Fields Constructors Methods
org.jruby.util.collections

public Class WeakHashSet<T>

extends Object
implements Set<T>, Cloneable
Class Inheritance
All Implemented Interfaces
java.lang.Cloneable, java.util.Set, java.util.Collection, java.lang.Iterable
Type Parameters
<T>
type
Imports
java.util.Collection, .Iterator, .Set, .WeakHashMap

A simple set that uses weak references to ensure that its elements can be garbage collected.
See Also
java.util.WeakHashMap, java.util.HashSet

Field Summary

Modifier and TypeField and Description
private final WeakHashMap<T, Object>
private static final Object

Constructor Summary

AccessConstructor and Description
public
public
WeakHashSet(int size)

Method Summary

Modifier and TypeMethod and Description
public boolean
add(T
element to be added to this set
o
)

Implements java.util.Set.add.

Adds the specified element to this set if it is not already present (optional operation).

public boolean
addAll(Collection<? extends T>
collection containing elements to be added to this set
coll
)

Implements java.util.Set.addAll.

Adds all of the elements in the specified collection to this set if they're not already present (optional operation).

public void
clear()

Implements java.util.Set.clear.

Removes all of the elements from this set (optional operation).

public WeakHashSet<T>
clone()

Overrides java.lang.Object.clone.

Creates and returns a copy of this object.

public boolean
contains(Object
element whose presence in this set is to be tested
o
)

Implements java.util.Set.contains.

Returns true if this set contains the specified element.

public boolean
containsAll(Collection<?>
collection to be checked for containment in this set
coll
)

Implements java.util.Set.containsAll.

Returns true if this set contains all of the elements of the specified collection.

public boolean
equals(final Object
object to be compared for equality with this set
o
)

Overrides java.lang.Object.equals.

Implements java.util.Set.equals.

Compares the specified object with this set for equality.

public int
hashCode()

Overrides java.lang.Object.hashCode.

Implements java.util.Set.hashCode.

Returns the hash code value for this set.

public boolean
isEmpty()

Implements java.util.Set.isEmpty.

Returns true if this set contains no elements.

public Iterator<T>
iterator()

Implements java.util.Set.iterator.

Returns an iterator over the elements in this set.

public boolean
remove(Object
object to be removed from this set, if present
o
)

Implements java.util.Set.remove.

Removes the specified element from this set if it is present (optional operation).

public boolean
removeAll(Collection<?>
collection containing elements to be removed from this set
coll
)

Implements java.util.Set.removeAll.

Removes from this set all of its elements that are contained in the specified collection (optional operation).

public boolean
retainAll(Collection<?>
collection containing elements to be retained in this set
coll
)

Implements java.util.Set.retainAll.

Retains only the elements in this set that are contained in the specified collection (optional operation).

public int
size()

Implements java.util.Set.size.

Returns the number of elements in this set (its cardinality).

public Object[]
toArray()

Implements java.util.Set.toArray.

Returns an array containing all of the elements in this set.

public <T> T[]
toArray(final T[]
the array into which the elements of this set are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purpose.
arr
)

Implements java.util.Set.toArray.

Returns an array containing all of the elements in this set; the runtime type of the returned array is that of the specified array.

public String
toString()

Overrides java.lang.Object.toString.

Returns a string representation of the object.

Inherited from java.lang.Object:
finalizegetClassnotifynotifyAllwaitwaitwait

Field Detail

mapback to summary
private final WeakHashMap<T, Object> map
PRESENTback to summary
private static final Object PRESENT

Constructor Detail

WeakHashSetback to summary
public WeakHashSet()
WeakHashSetback to summary
public WeakHashSet(int size)

Method Detail

addback to summary
public boolean add(T o)

Implements java.util.Set.add.

Doc from java.util.Set.add.

Adds the specified element to this set if it is not already present (optional operation). More formally, adds the specified element e to this set if the set contains no element e2 such that Objects.equals(e, e2). If this set already contains the element, the call leaves the set unchanged and returns false. In combination with the restriction on constructors, this ensures that sets never contain duplicate elements.

The stipulation above does not imply that sets must accept all elements; sets may refuse to add any particular element, including null, and throw an exception, as described in the specification for Collection.add. Individual set implementations should clearly document any restrictions on the elements that they may contain.

Parameters
o:T

element to be added to this set

Returns:boolean

true if this set did not already contain the specified element

addAllback to summary
public boolean addAll(Collection<? extends T> coll)

Implements java.util.Set.addAll.

Doc from java.util.Set.addAll.

Adds all of the elements in the specified collection to this set if they're not already present (optional operation). If the specified collection is also a set, the addAll operation effectively modifies this set so that its value is the union of the two sets. The behavior of this operation is undefined if the specified collection is modified while the operation is in progress.

Parameters
coll:Collection<? extends T>

collection containing elements to be added to this set

Returns:boolean

true if this set changed as a result of the call

clearback to summary
public void clear()

Implements java.util.Set.clear.

Doc from java.util.Set.clear.

Removes all of the elements from this set (optional operation). The set will be empty after this call returns.

cloneback to summary
public WeakHashSet<T> clone()

Overrides java.lang.Object.clone.

Doc from java.lang.Object.clone.

Creates and returns a copy of this object. The precise meaning of "copy" may depend on the class of the object. The general intent is that, for any object x, the expression:

x.clone() != x
will be true, and that the expression:
x.clone().getClass() == x.getClass()
will be true, but these are not absolute requirements. While it is typically the case that:
x.clone().equals(x)
will be true, this is not an absolute requirement.

By convention, the returned object should be obtained by calling super.clone. If a class and all of its superclasses (except Object) obey this convention, it will be the case that x.clone().getClass() == x.getClass().

By convention, the object returned by this method should be independent of this object (which is being cloned). To achieve this independence, it may be necessary to modify one or more fields of the object returned by super.clone before returning it. Typically, this means copying any mutable objects that comprise the internal "deep structure" of the object being cloned and replacing the references to these objects with references to the copies. If a class contains only primitive fields or references to immutable objects, then it is usually the case that no fields in the object returned by super.clone need to be modified.

Returns:WeakHashSet<T>

a clone of this instance.

Annotations
@Override
containsback to summary
public boolean contains(Object o)

Implements java.util.Set.contains.

Doc from java.util.Set.contains.

Returns true if this set contains the specified element. More formally, returns true if and only if this set contains an element e such that Objects.equals(o, e).

Parameters
o:Object

element whose presence in this set is to be tested

Returns:boolean

true if this set contains the specified element

containsAllback to summary
public boolean containsAll(Collection<?> coll)

Implements java.util.Set.containsAll.

Doc from java.util.Set.containsAll.

Returns true if this set contains all of the elements of the specified collection. If the specified collection is also a set, this method returns true if it is a subset of this set.

Parameters
coll:Collection<?>

collection to be checked for containment in this set

Returns:boolean

true if this set contains all of the elements of the specified collection

equalsback to summary
public boolean equals(final Object o)

Overrides java.lang.Object.equals.

Implements java.util.Set.equals.

Doc from java.util.Set.equals.

Compares the specified object with this set for equality. Returns true if the specified object is also a set, the two sets have the same size, and every member of the specified set is contained in this set (or equivalently, every member of this set is contained in the specified set). This definition ensures that the equals method works properly across different implementations of the set interface.

Parameters
o:Object

object to be compared for equality with this set

Returns:boolean

true if the specified object is equal to this set

Annotations
@Override
hashCodeback to summary
public int hashCode()

Overrides java.lang.Object.hashCode.

Implements java.util.Set.hashCode.

Doc from java.util.Set.hashCode.

Returns the hash code value for this set. The hash code of a set is defined to be the sum of the hash codes of the elements in the set, where the hash code of a null element is defined to be zero. This ensures that s1.equals(s2) implies that s1.hashCode()==s2.hashCode() for any two sets s1 and s2, as required by the general contract of Object#hashCode.

Returns:int

the hash code value for this set

Annotations
@Override
isEmptyback to summary
public boolean isEmpty()

Implements java.util.Set.isEmpty.

Doc from java.util.Set.isEmpty.

Returns true if this set contains no elements.

Returns:boolean

true if this set contains no elements

iteratorback to summary
public Iterator<T> iterator()

Implements java.util.Set.iterator.

Doc from java.util.Set.iterator.

Returns an iterator over the elements in this set. The elements are returned in no particular order (unless this set is an instance of some class that provides a guarantee).

Returns:Iterator<T>

an iterator over the elements in this set

removeback to summary
public boolean remove(Object o)

Implements java.util.Set.remove.

Doc from java.util.Set.remove.

Removes the specified element from this set if it is present (optional operation). More formally, removes an element e such that Objects.equals(o, e), if this set contains such an element. Returns true if this set contained the element (or equivalently, if this set changed as a result of the call). (This set will not contain the element once the call returns.)

Parameters
o:Object

object to be removed from this set, if present

Returns:boolean

true if this set contained the specified element

removeAllback to summary
public boolean removeAll(Collection<?> coll)

Implements java.util.Set.removeAll.

Doc from java.util.Set.removeAll.

Removes from this set all of its elements that are contained in the specified collection (optional operation). If the specified collection is also a set, this operation effectively modifies this set so that its value is the asymmetric set difference of the two sets.

Parameters
coll:Collection<?>

collection containing elements to be removed from this set

Returns:boolean

true if this set changed as a result of the call

retainAllback to summary
public boolean retainAll(Collection<?> coll)

Implements java.util.Set.retainAll.

Doc from java.util.Set.retainAll.

Retains only the elements in this set that are contained in the specified collection (optional operation). In other words, removes from this set all of its elements that are not contained in the specified collection. If the specified collection is also a set, this operation effectively modifies this set so that its value is the intersection of the two sets.

Parameters
coll:Collection<?>

collection containing elements to be retained in this set

Returns:boolean

true if this set changed as a result of the call

sizeback to summary
public int size()

Implements java.util.Set.size.

Doc from java.util.Set.size.

Returns the number of elements in this set (its cardinality). If this set contains more than Integer.MAX_VALUE elements, returns Integer.MAX_VALUE.

Returns:int

the number of elements in this set (its cardinality)

toArrayback to summary
public Object[] toArray()

Implements java.util.Set.toArray.

Doc from java.util.Set.toArray.

Returns an array containing all of the elements in this set. If this set makes any guarantees as to what order its elements are returned by its iterator, this method must return the elements in the same order.

The returned array will be "safe" in that no references to it are maintained by this set. (In other words, this method must allocate a new array even if this set is backed by an array). The caller is thus free to modify the returned array.

This method acts as bridge between array-based and collection-based APIs.

Returns:Object[]

an array containing all the elements in this set

toArrayback to summary
public <T> T[] toArray(final T[] arr)

Implements java.util.Set.toArray.

Doc from java.util.Set.toArray.

Returns an array containing all of the elements in this set; the runtime type of the returned array is that of the specified array. If the set fits in the specified array, it is returned therein. Otherwise, a new array is allocated with the runtime type of the specified array and the size of this set.

If this set fits in the specified array with room to spare (i.e., the array has more elements than this set), the element in the array immediately following the end of the set is set to null. (This is useful in determining the length of this set only if the caller knows that this set does not contain any null elements.)

If this set makes any guarantees as to what order its elements are returned by its iterator, this method must return the elements in the same order.

Like the toArray() method, this method acts as bridge between array-based and collection-based APIs. Further, this method allows precise control over the runtime type of the output array, and may, under certain circumstances, be used to save allocation costs.

Suppose x is a set known to contain only strings. The following code can be used to dump the set into a newly allocated array of String:

    String[] y = x.toArray(new String[0]);
Note that toArray(new Object[0]) is identical in function to toArray().
Parameters
<T>

Doc from java.util.Collection.toArray. the component type of the array to contain the collection

arr:T[]

the array into which the elements of this set are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purpose.

Returns:T[]

an array containing all the elements in this set

toStringback to summary
public String toString()

Overrides java.lang.Object.toString.

Doc from java.lang.Object.toString.

Returns a string representation of the object. Satisfying this method's contract implies a non-null result must be returned.

Returns:String

a string representation of the object

Annotations
@Override