- Type Parameters:
E- the type of the elements in the collection
- Direct Known Subclasses:
public abstract class AbstractCollectionDecorator<E> extends Object implements Collection<E>, SerializableDecorates another
Collectionto provide additional behaviour.
Each method call made on this
Collectionis forwarded to the decorated
Collection. This class is used as a framework on which to build to extensions such as synchronized and unmodifiable behaviour. The main advantage of decoration is that one decorator can wrap any implementation of
Collection, whereas sub-classing requires a new class to be written for each implementation.
This implementation does not perform any special processing with
iterator(). Instead it simply returns the value from the wrapped collection. This may be undesirable, for example if you are trying to write an unmodifiable implementation it might provide a loophole.
This implementation does not forward the hashCode and equals methods through to the backing object, but relies on Object's implementation. This is necessary to preserve the symmetry of equals. Custom definitions of equality are usually based on an interface, such as Set or List, so that the implementation of equals can cast the object being tested for equality to the custom interface. AbstractCollectionDecorator does not implement such custom interfaces directly; they are implemented only in subclasses. Therefore, forwarding equals would break symmetry, as the forwarding object might consider itself equal to the object being tested, but the reverse could not be true. This behavior is consistent with the JDK's collection wrappers, such as
Collections.unmodifiableCollection(Collection). Use an interface-specific subclass of AbstractCollectionDecorator, such as AbstractListDecorator, to preserve equality behavior, or override equals directly.
- See Also:
- Serialized Form
All Methods Instance Methods Concrete Methods Modifier and Type Method Description
addAll(Collection<? extends E> coll)
removeIf(Predicate<? super E> filter)
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, wait, wait, wait
Methods inherited from interface java.util.Collection
equals, hashCode, parallelStream, spliterator, stream, toArray
public boolean addAll(Collection<? extends E> coll)
public boolean containsAll(Collection<?> coll)
public boolean removeAll(Collection<?> coll)
public boolean retainAll(Collection<?> coll)