com.google.common.collect
Class ForwardingCollection<E>

java.lang.Object
  com.google.common.collect.ForwardingObject
      com.google.common.collect.ForwardingCollection<E>

All Implemented Interfaces:

java.io.Serializable, java.lang.Iterable<E>, java.util.Collection<E>

Direct Known Subclasses:

ForwardingList, ForwardingMultiset, ForwardingQueue, ForwardingSet

public abstract class ForwardingCollection<E>
extends ForwardingObject
implements java.util.Collection<E>

A collection which forwards all its method calls to another collection. Subclasses should override one or more methods to modify the behavior of the backing collection as desired per the decorator pattern.

Author:

Kevin Bourrillion

See Also:

ForwardingObject, Serialized Form

Constructor Summary

protected

ForwardingCollection(java.util.Collection<E> delegate) Constructs a forwarding collection that forwards to the provided delegate.

Method Summary

boolean	add(E element)
boolean	addAll(java.util.Collection<? extends E> collection)
void	clear()
boolean	contains(java.lang.Object object)
boolean	containsAll(java.util.Collection<?> collection)
protected static boolean	containsAllImpl(java.util.Collection<?> c, java.util.Collection<?> d) Returns true if the specified collection c contains all of the elements in the specified collection d.
protected static boolean	containsImpl(java.util.Collection<?> c, java.lang.Object o) Returns true if the specified collection c contains the element o.
protected java.util.Collection<E>	delegate() Returns the backing delegate object.
boolean	isEmpty()
java.util.Iterator<E>	iterator()
boolean	remove(java.lang.Object object)
boolean	removeAll(java.util.Collection<?> collection)
protected static boolean	removeAllImpl(java.util.Collection<?> c, java.util.Collection<?> d) Removes from the specified collection c all of its elements that are contained in the specified collection d (optional operation).
protected static boolean	removeImpl(java.util.Collection<?> c, java.lang.Object o) Removes from the specified collection c the specified element o (optional operation).
boolean	retainAll(java.util.Collection<?> c)
protected static boolean	retainAllImpl(java.util.Collection<?> c, java.util.Collection<?> d) Retains only the elements in the specified collection c that are contained in the specified collection d (optional operation).
int	size()
java.lang.Object[]	toArray()
<T> T[]	toArray(T[] array)
protected static java.lang.Object[]	toArrayImpl(java.util.Collection<?> c) Returns an array containing all of the elements in the specified collection.
protected static <T> T[]	toArrayImpl(java.util.Collection<?> c, T[] array) Returns an array containing all of the elements in the specified collection; the runtime type of the returned array is that of the specified array.
protected static java.lang.String	toStringImpl(java.util.Collection<?> c) Returns a string representation of the specified collection.

Methods inherited from class com.google.common.collect.ForwardingObject

toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Collection

equals, hashCode

Constructor Detail

ForwardingCollection

protected ForwardingCollection(java.util.Collection<E> delegate)

Constructs a forwarding collection that forwards to the provided delegate.

Method Detail

delegate

protected java.util.Collection<E> delegate()

Description copied from class: ForwardingObject

Returns the backing delegate object. This method should be overridden to specify the correct return type. For example:

  @SuppressWarnings("unchecked")
  @Override protected Foo delegate() {
    return (Foo) super.delegate();
  }

This method should always return the same delegate instance that was passed to the constructor.

Overrides:

delegate in class ForwardingObject

iterator

public java.util.Iterator<E> iterator()

Specified by:

iterator in interface java.lang.Iterable<E>

Specified by:

iterator in interface java.util.Collection<E>

size

public int size()

Specified by:

size in interface java.util.Collection<E>

removeAll

public boolean removeAll(java.util.Collection<?> collection)

Specified by:

removeAll in interface java.util.Collection<E>

isEmpty

public boolean isEmpty()

Specified by:

isEmpty in interface java.util.Collection<E>

contains

public boolean contains(java.lang.Object object)

Specified by:

contains in interface java.util.Collection<E>

toArray

public java.lang.Object[] toArray()

Specified by:

toArray in interface java.util.Collection<E>

toArray

public <T> T[] toArray(T[] array)

Specified by:

toArray in interface java.util.Collection<E>

add

public boolean add(E element)

Specified by:

add in interface java.util.Collection<E>

remove

public boolean remove(java.lang.Object object)

Specified by:

remove in interface java.util.Collection<E>

containsAll

public boolean containsAll(java.util.Collection<?> collection)

Specified by:

containsAll in interface java.util.Collection<E>

addAll

public boolean addAll(java.util.Collection<? extends E> collection)

Specified by:

addAll in interface java.util.Collection<E>

retainAll

public boolean retainAll(java.util.Collection<?> c)

Specified by:

retainAll in interface java.util.Collection<E>

clear

public void clear()

Specified by:

clear in interface java.util.Collection<E>

toArrayImpl

protected static java.lang.Object[] toArrayImpl(java.util.Collection<?> c)

Returns an array containing all of the elements in the specified collection. This method returns the elements in the order they are returned by the collection's iterator. The returned array is "safe" in that no references to it are maintained by the collection. The caller is thus free to modify the returned array.

Parameters:

c - the collection for which to return an array of elements

See Also:

AbstractCollection.toArray()

toArrayImpl

protected static <T> T[] toArrayImpl(java.util.Collection<?> c,
                                     T[] array)

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

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

This method returns the elements in the order they are returned by the collection's iterator.

Parameters:

c - the collection for which to return an array of elements

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

Throws:

java.lang.ArrayStoreException - if the runtime type of the specified array is not a supertype of the runtime type of every element in the specified collection

See Also:

AbstractCollection.toArray(Object[])

toStringImpl

protected static java.lang.String toStringImpl(java.util.Collection<?> c)

Returns a string representation of the specified collection. The string representation consists of a list of the collection's elements in the order they are returned by its iterator, enclosed in square brackets ("[]"). Adjacent elements are separated by the characters ", " (comma and space). Elements are converted to strings as by String.valueOf(Object).

Parameters:

c - the collection for which to return a string representation

See Also:

AbstractCollection.toString()

containsImpl

protected static boolean containsImpl(java.util.Collection<?> c,
                                      @Nullable
                                      java.lang.Object o)

Returns true if the specified collection c contains the element o.

This method iterates over the specified collection c, checking each element returned by the iterator in turn to see if it equals the provided object o. If any element is equal, true is returned, otherwise false is returned.

Parameters:

c - a collection which might contain the element.

o - an element that might be contained by c

containsAllImpl

protected static boolean containsAllImpl(java.util.Collection<?> c,
                                         java.util.Collection<?> d)

Returns true if the specified collection c contains all of the elements in the specified collection d.

This method iterates over the specified collection d, checking each element returned by the iterator in turn to see if it is contained in the specified collection c. If all elements are so contained, true is returned, otherwise false.

Parameters:

c - a collection which might contain all elements in d

d - a collection whose elements might be contained by c

See Also:

AbstractCollection.containsAll(Collection)

removeImpl

protected static boolean removeImpl(java.util.Collection<?> c,
                                    @Nullable
                                    java.lang.Object o)

Removes from the specified collection c the specified element o (optional operation).

This method iterates over the collection c, checking each element returned by the iterator in turn to see if it equal to the provided element o. If they are equal, it is removed from the collection c with the iterator's remove method

Parameters:

c - the collection from which to remove

o - an element to remove from the collectoin

Returns:

true if collection c changed as a result

Throws:

java.lang.UnsupportedOperationException - if c's iterator does not support the remove method and c contains one or more elements in common with d

removeAllImpl

protected static boolean removeAllImpl(java.util.Collection<?> c,
                                       java.util.Collection<?> d)

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

This method iterates over the collection c, checking each element returned by the iterator in turn to see if it is contained in the collection d. If it is so contained, it is removed from the collection c with the iterator's remove method.

Parameters:

c - the collection from which to remove

d - a collection of elements to remove from collection c

Returns:

true if collection c changed as a result

Throws:

java.lang.UnsupportedOperationException - if c's iterator does not support the remove method and c contains one or more elements in common with d

See Also:

AbstractCollection.removeAll(Collection)

retainAllImpl

protected static boolean retainAllImpl(java.util.Collection<?> c,
                                       java.util.Collection<?> d)

Retains only the elements in the specified collection c that are contained in the specified collection d (optional operation). In other words, removes from the collection c all of its elements that are not contained in the collection d.

This implementation iterates over the collection c, checking each element returned by the iterator in turn to see if it is contained in the collection d. If it is not so contained, it is removed from the collection c with the iterator's remove method.

Parameters:

c - the collection from which to remove

d - a collection of elements to retain in collection c

Returns:

true if collection c changed as a result

Throws:

java.lang.UnsupportedOperationException - if c's iterator does not support the remove method and c contains one or more elements not present in the d