Retains only the elements in this collection that are contained in the
specified collection (optional operation). In other words, removes from
this collection all of its elements that are not contained in the
specified collection.
@param c collection containing elements to be retained in this collection
@return <tt>true</tt> if this collection changed as a result of the call
@throws UnsupportedOperationException if the <tt>retainAll</tt> operation
is not supported by this collection
@throws ClassCastException if the types of one or more elements
in this collection are incompatible with the specified
collection
(<a href="#optional-restrictions">optional</a>)
@throws NullPointerException if this collection contains one or more
null elements and the specified collection does not permit null
elements
(<a href="#optional-restrictions">optional</a>),
or if the specified collection is null
@see #remove(Object)
@see #contains(Object)
Retains only the elements in this collection that are contained in the specified collection (optional operation). In other words, removes from this collection all of its elements that are not contained in the specified collection.
@param c collection containing elements to be retained in this collection @return <tt>true</tt> if this collection changed as a result of the call @throws UnsupportedOperationException if the <tt>retainAll</tt> operation is not supported by this collection @throws ClassCastException if the types of one or more elements in this collection are incompatible with the specified collection (<a href="#optional-restrictions">optional</a>) @throws NullPointerException if this collection contains one or more null elements and the specified collection does not permit null elements (<a href="#optional-restrictions">optional</a>), or if the specified collection is null @see #remove(Object) @see #contains(Object)