Class ForwardingCollection<E extends @Nullable Object>

java.lang.Object

com.google.common.collect.ForwardingObject

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

All Implemented Interfaces:

Iterable<E>, Collection<E>

Direct Known Subclasses:

ForwardingList, ForwardingMultiset, ForwardingQueue, ForwardingSet

@GwtCompatible
public abstract class ForwardingCollection<E extends @Nullable Object>
extends ForwardingObject
implements 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.

Warning: The methods of ForwardingCollection forward indiscriminately to the methods of the delegate. For example, overriding add(E) alone will not change the behavior of addAll(java.util.Collection<? extends E>), which can lead to unexpected behavior. In this case, you should override addAll as well, either providing your own implementation, or delegating to the provided standardAddAll method.

default method warning: This class does not forward calls to default methods. Instead, it inherits their default implementations. When those implementations invoke methods, they invoke methods on the ForwardingCollection.

The standard methods are not guaranteed to be thread-safe, even when all of the methods that they depend on are thread-safe.

Since:

2.0

Author:

Kevin Bourrillion, Louis Wasserman

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	ForwardingCollection()	Constructor for use by subclasses.

Method Summary

Modifier and Type	Method	Description
boolean	add(E element)
boolean	addAll(Collection<? extends E> collection)
void	clear()
boolean	contains(@Nullable Object object)
boolean	containsAll(Collection<?> collection)
protected abstract Collection<E>	delegate()	Returns the backing delegate instance that methods are forwarded to.
boolean	isEmpty()
Iterator<E>	iterator()
boolean	remove(@Nullable Object object)
boolean	removeAll(Collection<?> collection)
boolean	retainAll(Collection<?> collection)
int	size()
protected boolean	standardAddAll(Collection<? extends E> collection)	A sensible definition of addAll(java.util.Collection<? extends E>) in terms of add(E).
protected void	standardClear()	A sensible definition of clear() in terms of iterator(), using the iterator's remove method.
protected boolean	standardContains(@Nullable Object object)	A sensible definition of contains(java.lang.Object) in terms of iterator().
protected boolean	standardContainsAll(Collection<?> collection)	A sensible definition of containsAll(java.util.Collection<?>) in terms of contains(java.lang.Object) .
protected boolean	standardIsEmpty()	A sensible definition of isEmpty() as !iterator().hasNext.
protected boolean	standardRemove(@Nullable Object object)	A sensible definition of remove(java.lang.Object) in terms of iterator(), using the iterator's remove method.
protected boolean	standardRemoveAll(Collection<?> collection)	A sensible definition of removeAll(java.util.Collection<?>) in terms of iterator(), using the iterator's remove method.
protected boolean	standardRetainAll(Collection<?> collection)	A sensible definition of retainAll(java.util.Collection<?>) in terms of iterator(), using the iterator's remove method.
protected @Nullable Object[]	standardToArray()	A sensible definition of toArray() in terms of toArray(Object[]).
protected <T extends @Nullable Object> T[]	standardToArray(T[] array)	A sensible definition of toArray(Object[]) in terms of size() and iterator().
protected String	standardToString()	A sensible definition of ForwardingObject.toString() in terms of iterator().
@Nullable Object[]	toArray()
<T extends @Nullable Object> T[]	toArray(T[] array)

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, parallelStream, removeIf, spliterator, stream, toArray

Methods inherited from interface java.lang.Iterable

forEach

Constructor Details

ForwardingCollection

protected ForwardingCollection()

Constructor for use by subclasses.

Method Details

delegate

protected abstract Collection<E> delegate()

Description copied from class: ForwardingObject

Returns the backing delegate instance that methods are forwarded to. Abstract subclasses generally override this method with an abstract method that has a more specific return type, such as ForwardingSet.delegate(). Concrete subclasses override this method to supply the instance being decorated.

Specified by:

delegate in class ForwardingObject

iterator

public Iterator<E> iterator()

Specified by:

iterator in interface Collection<E extends @Nullable Object>

Specified by:

iterator in interface Iterable<E extends @Nullable Object>

size

public int size()

Specified by:

size in interface Collection<E extends @Nullable Object>

removeAll

@CanIgnoreReturnValue
public boolean removeAll(Collection<?> collection)

Specified by:

removeAll in interface Collection<E extends @Nullable Object>

isEmpty

public boolean isEmpty()

Specified by:

isEmpty in interface Collection<E extends @Nullable Object>

contains

public boolean contains(@Nullable Object object)

Specified by:

contains in interface Collection<E extends @Nullable Object>

add

@CanIgnoreReturnValue
public boolean add(E element)

Specified by:

add in interface Collection<E extends @Nullable Object>

remove

@CanIgnoreReturnValue
public boolean remove(@Nullable Object object)

Specified by:

remove in interface Collection<E extends @Nullable Object>

containsAll

public boolean containsAll(Collection<?> collection)

Specified by:

containsAll in interface Collection<E extends @Nullable Object>

addAll

@CanIgnoreReturnValue
public boolean addAll(Collection<? extends E> collection)

Specified by:

addAll in interface Collection<E extends @Nullable Object>

retainAll

@CanIgnoreReturnValue
public boolean retainAll(Collection<?> collection)

Specified by:

retainAll in interface Collection<E extends @Nullable Object>

clear

public void clear()

Specified by:

clear in interface Collection<E extends @Nullable Object>

toArray

public @Nullable Object[] toArray()

Specified by:

toArray in interface Collection<E extends @Nullable Object>

toArray

@CanIgnoreReturnValue
public <T extends @Nullable Object> T[] toArray(T[] array)

Specified by:

toArray in interface Collection<E extends @Nullable Object>

standardContains

protected boolean standardContains(@Nullable Object object)

A sensible definition of contains(java.lang.Object) in terms of iterator(). If you override iterator(), you may wish to override contains(java.lang.Object) to forward to this implementation.

Since:

7.0

standardContainsAll

protected boolean standardContainsAll(Collection<?> collection)

A sensible definition of containsAll(java.util.Collection<?>) in terms of contains(java.lang.Object) . If you override contains(java.lang.Object), you may wish to override containsAll(java.util.Collection<?>) to forward to this implementation.

Since:

7.0

standardAddAll

protected boolean standardAddAll(Collection<? extends E> collection)

A sensible definition of addAll(java.util.Collection<? extends E>) in terms of add(E). If you override add(E), you may wish to override addAll(java.util.Collection<? extends E>) to forward to this implementation.

Since:

7.0

standardRemove

protected boolean standardRemove(@Nullable Object object)

A sensible definition of remove(java.lang.Object) in terms of iterator(), using the iterator's remove method. If you override iterator(), you may wish to override remove(java.lang.Object) to forward to this implementation.

Since:

7.0

standardRemoveAll

protected boolean standardRemoveAll(Collection<?> collection)

A sensible definition of removeAll(java.util.Collection<?>) in terms of iterator(), using the iterator's remove method. If you override iterator(), you may wish to override removeAll(java.util.Collection<?>) to forward to this implementation.

Since:

7.0

standardRetainAll

protected boolean standardRetainAll(Collection<?> collection)

A sensible definition of retainAll(java.util.Collection<?>) in terms of iterator(), using the iterator's remove method. If you override iterator(), you may wish to override retainAll(java.util.Collection<?>) to forward to this implementation.

Since:

7.0

standardClear

protected void standardClear()

A sensible definition of clear() in terms of iterator(), using the iterator's remove method. If you override iterator(), you may wish to override clear() to forward to this implementation.

Since:

7.0

standardIsEmpty

protected boolean standardIsEmpty()

A sensible definition of isEmpty() as !iterator().hasNext. If you override isEmpty(), you may wish to override isEmpty() to forward to this implementation. Alternately, it may be more efficient to implement isEmpty as size() == 0.

Since:

7.0

standardToString

protected String standardToString()

A sensible definition of ForwardingObject.toString() in terms of iterator(). If you override iterator(), you may wish to override ForwardingObject.toString() to forward to this implementation.

Since:

7.0

standardToArray

protected @Nullable Object[] standardToArray()

A sensible definition of toArray() in terms of toArray(Object[]). If you override toArray(Object[]), you may wish to override toArray() to forward to this implementation.

Since:

7.0

standardToArray

protected <T extends @Nullable Object> T[] standardToArray(T[] array)

A sensible definition of toArray(Object[]) in terms of size() and iterator(). If you override either of these methods, you may wish to override toArray() to forward to this implementation.

Since:

7.0