@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) |
toString
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
equals, hashCode, parallelStream, removeIf, spliterator, stream
protected ForwardingCollection()
Constructor for use by subclasses.
protected abstract Collection<E> delegate()
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.
delegate
in class ForwardingObject
public 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.