@GwtCompatible public abstract class ForwardingCollection<E> 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.
The standard methods are not guaranteed to be thread-safe, even when all of the methods that they depend on are thread-safe.
| Modifier | Constructor and Description |
|---|---|
protected |
ForwardingCollection()
Constructor for use by subclasses.
|
| Modifier and Type | Method and 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()
|
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 Object[] |
standardToArray()
A sensible definition of
toArray() in terms of toArray(Object[]). |
protected <T> T[] |
standardToArray(T[] array)
|
protected String |
standardToString()
A sensible definition of
ForwardingObject.toString() in terms of iterator(). |
Object[] |
toArray() |
<T> T[] |
toArray(T[] array) |
toStringclone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, waitequals, hashCode, parallelStream, removeIf, spliterator, streamprotected ForwardingCollection()
Constructor for use by subclasses.
protected abstract Collection<E> delegate()
ForwardingObjectReturns 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.
delegate in class ForwardingObjectpublic int size()
size in interface Collection<E>public boolean removeAll(Collection<?> collection)
removeAll in interface Collection<E>public boolean isEmpty()
isEmpty in interface Collection<E>public boolean contains(Object object)
contains in interface Collection<E>public boolean add(E element)
add in interface Collection<E>public boolean remove(Object object)
remove in interface Collection<E>public boolean containsAll(Collection<?> collection)
containsAll in interface Collection<E>public boolean addAll(Collection<? extends E> collection)
addAll in interface Collection<E>public boolean retainAll(Collection<?> collection)
retainAll in interface Collection<E>public void clear()
clear in interface Collection<E>public Object[] toArray()
toArray in interface Collection<E>public <T> T[] toArray(T[] array)
toArray in interface Collection<E>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.
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.
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.
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.
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.
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.
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.
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.
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.
protected 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.
protected <T> 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.