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

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method	Description
`boolean`	`add(E element)`
`boolean`	`addAll(Collection<? extends E> collection)`
`void`	`clear()`
`boolean`	`contains(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(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(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(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 Detail
  - ForwardingCollection
```
protected ForwardingCollection()
```
    Constructor for use by subclasses.
- Method Detail
  - 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(@CheckForNull
                        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(@CheckForNull
                      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(@CheckForNull
                                   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(@CheckForNull
                                 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

Class ForwardingCollection<E extends @Nullable Object>

Constructor Summary

Method Summary

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

Methods inherited from class java.lang.Object

Methods inherited from interface java.util.Collection

Methods inherited from interface java.lang.Iterable

Constructor Detail

ForwardingCollection

Method Detail

delegate

iterator

size

removeAll

isEmpty

contains

add

remove

containsAll

addAll

retainAll

clear

toArray

toArray

standardContains

standardContainsAll

standardAddAll

standardRemove

standardRemoveAll

standardRetainAll

standardClear

standardIsEmpty

standardToString

standardToArray

standardToArray