Package Summary Overview Summary

### class:LinkedBlockingDeque [NONE]
Type Parameters: `E` - the type of elements held in this deque All Implemented Interfaces: `Serializable`, `Iterable<E>`, `Collection<E>`, `BlockingDeque<E>`, `BlockingQueue<E>`, `Deque<E>`, `Queue<E>` public class LinkedBlockingDeque<E>extends AbstractQueue<E> implements BlockingDeque<E>, Serializable An optionally-bounded blocking deque based on linked nodes. The optional capacity bound constructor argument serves as a way to prevent excessive expansion. The capacity, if unspecified, is equal to `Integer.MAX_VALUE`. Linked nodes are dynamically created upon each insertion unless this would bring the deque above capacity. Most operations run in constant time (ignoring time spent blocking). Exceptions include `remove`, `removeFirstOccurrence`, `removeLastOccurrence`, `contains`, `iterator.remove()`, and the bulk operations, all of which run in linear time. This class and its iterator implement all of the optional methods of the `Collection` and `Iterator` interfaces. This class is a member of the Java Collections Framework . Since: 1.6 See Also: Serialized Form

### constructor:LinkedBlockingDeque() [NONE]
### LinkedBlockingDeque public LinkedBlockingDeque() Creates a `LinkedBlockingDeque` with a capacity of `Integer.MAX_VALUE`.

### constructor:LinkedBlockingDeque(int) [NONE]
### LinkedBlockingDeque public LinkedBlockingDeque (int capacity) Creates a `LinkedBlockingDeque` with the given (fixed) capacity. Parameters: `capacity` - the capacity of this deque Throws: `IllegalArgumentException` - if `capacity` is less than 1

### constructor:LinkedBlockingDeque(java.util.Collection) [NONE]
### LinkedBlockingDeque public LinkedBlockingDeque (Collection<? extends E> c) Creates a `LinkedBlockingDeque` with a capacity of `Integer.MAX_VALUE`, initially containing the elements of the given collection, added in traversal order of the collection's iterator. Parameters: `c` - the collection of elements to initially contain Throws: `NullPointerException` - if the specified collection or any of its elements are null

### method:removeFirst() [NONE]
### removeFirst public E removeFirst() Description copied from interface: `Deque` Retrieves and removes the first element of this deque. This method differs from `pollFirst` only in that it throws an exception if this deque is empty. Specified by: `removeFirst` in interface `Deque<E>` Returns: the head of this deque Throws: `NoSuchElementException` - if this deque is empty

### method:removeLast() [NONE]
### removeLast public E removeLast() Description copied from interface: `Deque` Retrieves and removes the last element of this deque. This method differs from `pollLast` only in that it throws an exception if this deque is empty. Specified by: `removeLast` in interface `Deque<E>` Returns: the tail of this deque Throws: `NoSuchElementException` - if this deque is empty

### method:pollFirst() [NONE]
### pollFirst public E pollFirst() Description copied from interface: `Deque` Retrieves and removes the first element of this deque, or returns `null` if this deque is empty. Specified by: `pollFirst` in interface `Deque<E>` Returns: the head of this deque, or `null` if this deque is empty

### method:pollLast() [NONE]
### pollLast public E pollLast() Description copied from interface: `Deque` Retrieves and removes the last element of this deque, or returns `null` if this deque is empty. Specified by: `pollLast` in interface `Deque<E>` Returns: the tail of this deque, or `null` if this deque is empty

### method:takeFirst() [NONE]
### takeFirst public E takeFirst() throws InterruptedException Description copied from interface: `BlockingDeque` Retrieves and removes the first element of this deque, waiting if necessary until an element becomes available. Specified by: `takeFirst` in interface `BlockingDeque<E>` Returns: the head of this deque Throws: `InterruptedException` - if interrupted while waiting

### method:takeLast() [NONE]
### takeLast public E takeLast() throws InterruptedException Description copied from interface: `BlockingDeque` Retrieves and removes the last element of this deque, waiting if necessary until an element becomes available. Specified by: `takeLast` in interface `BlockingDeque<E>` Returns: the tail of this deque Throws: `InterruptedException` - if interrupted while waiting

### method:pollFirst(long,java.util.concurrent.TimeUnit) [NONE]
### pollFirst public E pollFirst (long timeout, TimeUnit unit) throws InterruptedException Description copied from interface: `BlockingDeque` Retrieves and removes the first element of this deque, waiting up to the specified wait time if necessary for an element to become available. Specified by: `pollFirst` in interface `BlockingDeque<E>` Parameters: `timeout` - how long to wait before giving up, in units of `unit` `unit` - a `TimeUnit` determining how to interpret the `timeout` parameter Returns: the head of this deque, or `null` if the specified waiting time elapses before an element is available Throws: `InterruptedException` - if interrupted while waiting

### method:pollLast(long,java.util.concurrent.TimeUnit) [NONE]
### pollLast public E pollLast (long timeout, TimeUnit unit) throws InterruptedException Description copied from interface: `BlockingDeque` Retrieves and removes the last element of this deque, waiting up to the specified wait time if necessary for an element to become available. Specified by: `pollLast` in interface `BlockingDeque<E>` Parameters: `timeout` - how long to wait before giving up, in units of `unit` `unit` - a `TimeUnit` determining how to interpret the `timeout` parameter Returns: the tail of this deque, or `null` if the specified waiting time elapses before an element is available Throws: `InterruptedException` - if interrupted while waiting

### method:getFirst() [NONE]
### getFirst public E getFirst() Description copied from interface: `Deque` Retrieves, but does not remove, the first element of this deque. This method differs from `peekFirst` only in that it throws an exception if this deque is empty. Specified by: `getFirst` in interface `Deque<E>` Returns: the head of this deque Throws: `NoSuchElementException` - if this deque is empty

### method:getLast() [NONE]
### getLast public E getLast() Description copied from interface: `Deque` Retrieves, but does not remove, the last element of this deque. This method differs from `peekLast` only in that it throws an exception if this deque is empty. Specified by: `getLast` in interface `Deque<E>` Returns: the tail of this deque Throws: `NoSuchElementException` - if this deque is empty

### method:peekFirst() [NONE]
### peekFirst public E peekFirst() Description copied from interface: `Deque` Retrieves, but does not remove, the first element of this deque, or returns `null` if this deque is empty. Specified by: `peekFirst` in interface `Deque<E>` Returns: the head of this deque, or `null` if this deque is empty

### method:peekLast() [NONE]
### peekLast public E peekLast() Description copied from interface: `Deque` Retrieves, but does not remove, the last element of this deque, or returns `null` if this deque is empty. Specified by: `peekLast` in interface `Deque<E>` Returns: the tail of this deque, or `null` if this deque is empty

### method:removeFirstOccurrence(java.lang.Object) [NONE]
### removeFirstOccurrence public boolean removeFirstOccurrence (Object o) Description copied from interface: `BlockingDeque` Removes the first occurrence of the specified element from this deque. If the deque does not contain the element, it is unchanged. More formally, removes the first element `e` such that `o.equals(e)` (if such an element exists). Returns `true` if this deque contained the specified element (or equivalently, if this deque changed as a result of the call). Specified by: `removeFirstOccurrence` in interface `BlockingDeque<E>` Specified by: `removeFirstOccurrence` in interface `Deque<E>` Parameters: `o` - element to be removed from this deque, if present Returns: `true` if an element was removed as a result of this call

### method:removeLastOccurrence(java.lang.Object) [NONE]
### removeLastOccurrence public boolean removeLastOccurrence (Object o) Description copied from interface: `BlockingDeque` Removes the last occurrence of the specified element from this deque. If the deque does not contain the element, it is unchanged. More formally, removes the last element `e` such that `o.equals(e)` (if such an element exists). Returns `true` if this deque contained the specified element (or equivalently, if this deque changed as a result of the call). Specified by: `removeLastOccurrence` in interface `BlockingDeque<E>` Specified by: `removeLastOccurrence` in interface `Deque<E>` Parameters: `o` - element to be removed from this deque, if present Returns: `true` if an element was removed as a result of this call ### add public boolean add (E e) Inserts the specified element at the end of this deque unless it would violate capacity restrictions. When using a capacity-restricted deque, it is generally preferable to use method `offer`. This method is equivalent to `addLast(E)`. Specified by: `add` in interface `BlockingDeque<E>` Specified by: `add` in interface `BlockingQueue<E>` Specified by: `add` in interface `Collection<E>` Specified by: `add` in interface `Deque<E>` Specified by: `add` in interface `Queue<E>` Overrides: `add` in class `AbstractQueue<E>` Parameters: `e` - the element to add Returns: `true` (as specified by `Collection.add(E)`) Throws: `IllegalStateException` - if this deque is full `NullPointerException` - if the specified element is null ### offer public boolean offer (E e) Description copied from interface: `BlockingDeque` Inserts the specified element into the queue represented by this deque (in other words, at the tail of this deque) if it is possible to do so immediately without violating capacity restrictions, returning `true` upon success and `false` if no space is currently available. When using a capacity-restricted deque, this method is generally preferable to the `BlockingDeque.add(E)` method, which can fail to insert an element only by throwing an exception. This method is equivalent to `offerLast`. Specified by: `offer` in interface `BlockingDeque<E>` Specified by: `offer` in interface `BlockingQueue<E>` Specified by: `offer` in interface `Deque<E>` Specified by: `offer` in interface `Queue<E>` Parameters: `e` - the element to add Returns: `true` if the element was added to this queue, else `false` Throws: `NullPointerException` - if the specified element is null ### put public void put (E e) throws InterruptedException Description copied from interface: `BlockingDeque` Inserts the specified element into the queue represented by this deque (in other words, at the tail of this deque), waiting if necessary for space to become available. This method is equivalent to `putLast`. Specified by: `put` in interface `BlockingDeque<E>` Specified by: `put` in interface `BlockingQueue<E>` Parameters: `e` - the element to add Throws: `NullPointerException` - if the specified element is null `InterruptedException` - if interrupted while waiting ### offer public boolean offer (E e, long timeout, TimeUnit unit) throws InterruptedException Description copied from interface: `BlockingDeque` Inserts the specified element into the queue represented by this deque (in other words, at the tail of this deque), waiting up to the specified wait time if necessary for space to become available. This method is equivalent to `offerLast`. Specified by: `offer` in interface `BlockingDeque<E>` Specified by: `offer` in interface `BlockingQueue<E>` Parameters: `e` - the element to add `timeout` - how long to wait before giving up, in units of `unit` `unit` - a `TimeUnit` determining how to interpret the `timeout` parameter Returns: `true` if the element was added to this deque, else `false` Throws: `NullPointerException` - if the specified element is null `InterruptedException` - if interrupted while waiting

### method:remove() [NONE]
### remove public E remove() Retrieves and removes the head of the queue represented by this deque. This method differs from `poll()` only in that it throws an exception if this deque is empty. This method is equivalent to `removeFirst`. Specified by: `remove` in interface `BlockingDeque<E>` Specified by: `remove` in interface `Deque<E>` Specified by: `remove` in interface `Queue<E>` Overrides: `remove` in class `AbstractQueue<E>` Returns: the head of the queue represented by this deque Throws: `NoSuchElementException` - if this deque is empty

### method:poll() [NONE]
### poll public E poll() Description copied from interface: `BlockingDeque` Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque), or returns `null` if this deque is empty. This method is equivalent to `Deque.pollFirst()`. Specified by: `poll` in interface `BlockingDeque<E>` Specified by: `poll` in interface `Deque<E>` Specified by: `poll` in interface `Queue<E>` Returns: the head of this deque, or `null` if this deque is empty

### method:take() [NONE]
### take public E take() throws InterruptedException Description copied from interface: `BlockingDeque` Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque), waiting if necessary until an element becomes available. This method is equivalent to `takeFirst`. Specified by: `take` in interface `BlockingDeque<E>` Specified by: `take` in interface `BlockingQueue<E>` Returns: the head of this deque Throws: `InterruptedException` - if interrupted while waiting

### method:poll(long,java.util.concurrent.TimeUnit) [NONE]
### poll public E poll (long timeout, TimeUnit unit) throws InterruptedException Description copied from interface: `BlockingDeque` Retrieves and removes the head of the queue represented by this deque (in other words, the first element of this deque), waiting up to the specified wait time if necessary for an element to become available. This method is equivalent to `pollFirst`. Specified by: `poll` in interface `BlockingDeque<E>` Specified by: `poll` in interface `BlockingQueue<E>` Parameters: `timeout` - how long to wait before giving up, in units of `unit` `unit` - a `TimeUnit` determining how to interpret the `timeout` parameter Returns: the head of this deque, or `null` if the specified waiting time elapses before an element is available Throws: `InterruptedException` - if interrupted while waiting

### method:element() [NONE]
### element public E element() Retrieves, but does not remove, the head of the queue represented by this deque. This method differs from `peek()` only in that it throws an exception if this deque is empty. This method is equivalent to `getFirst`. Specified by: `element` in interface `BlockingDeque<E>` Specified by: `element` in interface `Deque<E>` Specified by: `element` in interface `Queue<E>` Overrides: `element` in class `AbstractQueue<E>` Returns: the head of the queue represented by this deque Throws: `NoSuchElementException` - if this deque is empty

### method:peek() [NONE]
### peek public E peek() Description copied from interface: `BlockingDeque` Retrieves, but does not remove, the head of the queue represented by this deque (in other words, the first element of this deque), or returns `null` if this deque is empty. This method is equivalent to `peekFirst`. Specified by: `peek` in interface `BlockingDeque<E>` Specified by: `peek` in interface `Deque<E>` Specified by: `peek` in interface `Queue<E>` Returns: the head of this deque, or `null` if this deque is empty

### method:remainingCapacity() [NONE]
### remainingCapacity public int remainingCapacity() Returns the number of additional elements that this deque can ideally (in the absence of memory or resource constraints) accept without blocking. This is always equal to the initial capacity of this deque less the current `size` of this deque. Note that you cannot always tell if an attempt to insert an element will succeed by inspecting `remainingCapacity` because it may be the case that another thread is about to insert or remove an element. Specified by: `remainingCapacity` in interface `BlockingQueue<E>` Returns: the remaining capacity

### method:drainTo(java.util.Collection) [NONE]
### drainTo public int drainTo (Collection<? super E> c) Description copied from interface: `BlockingQueue` Removes all available elements from this queue and adds them to the given collection. This operation may be more efficient than repeatedly polling this queue. A failure encountered while attempting to add elements to collection `c` may result in elements being in neither, either or both collections when the associated exception is thrown. Attempts to drain a queue to itself result in `IllegalArgumentException`. Further, the behavior of this operation is undefined if the specified collection is modified while the operation is in progress. Specified by: `drainTo` in interface `BlockingQueue<E>` Parameters: `c` - the collection to transfer elements into Returns: the number of elements transferred Throws: `UnsupportedOperationException` - if addition of elements is not supported by the specified collection `ClassCastException` - if the class of an element of this queue prevents it from being added to the specified collection `NullPointerException` - if the specified collection is null `IllegalArgumentException` - if the specified collection is this queue, or some property of an element of this queue prevents it from being added to the specified collection

### method:drainTo(java.util.Collection,int) [NONE]
### drainTo public int drainTo (Collection<? super E> c, int maxElements) Description copied from interface: `BlockingQueue` Removes at most the given number of available elements from this queue and adds them to the given collection. A failure encountered while attempting to add elements to collection `c` may result in elements being in neither, either or both collections when the associated exception is thrown. Attempts to drain a queue to itself result in `IllegalArgumentException`. Further, the behavior of this operation is undefined if the specified collection is modified while the operation is in progress. Specified by: `drainTo` in interface `BlockingQueue<E>` Parameters: `c` - the collection to transfer elements into `maxElements` - the maximum number of elements to transfer Returns: the number of elements transferred Throws: `UnsupportedOperationException` - if addition of elements is not supported by the specified collection `ClassCastException` - if the class of an element of this queue prevents it from being added to the specified collection `NullPointerException` - if the specified collection is null `IllegalArgumentException` - if the specified collection is this queue, or some property of an element of this queue prevents it from being added to the specified collection ### push public void push (E e) Description copied from interface: `BlockingDeque` Pushes an element onto the stack represented by this deque (in other words, at the head of this deque) if it is possible to do so immediately without violating capacity restrictions, throwing an `IllegalStateException` if no space is currently available. This method is equivalent to `addFirst`. Specified by: `push` in interface `BlockingDeque<E>` Specified by: `push` in interface `Deque<E>` Parameters: `e` - the element to push Throws: `IllegalStateException` - if this deque is full `NullPointerException` - if the specified element is null

### method:pop() [NONE]
### pop public E pop() Description copied from interface: `Deque` Pops an element from the stack represented by this deque. In other words, removes and returns the first element of this deque. This method is equivalent to `Deque.removeFirst()`. Specified by: `pop` in interface `Deque<E>` Returns: the element at the front of this deque (which is the top of the stack represented by this deque) Throws: `NoSuchElementException` - if this deque is empty

### method:remove(java.lang.Object) [NONE]
### remove public boolean remove (Object o) Removes the first occurrence of the specified element from this deque. If the deque does not contain the element, it is unchanged. More formally, removes the first element `e` such that `o.equals(e)` (if such an element exists). Returns `true` if this deque contained the specified element (or equivalently, if this deque changed as a result of the call). This method is equivalent to `removeFirstOccurrence`. Specified by: `remove` in interface `BlockingDeque<E>` Specified by: `remove` in interface `BlockingQueue<E>` Specified by: `remove` in interface `Collection<E>` Specified by: `remove` in interface `Deque<E>` Overrides: `remove` in class `AbstractCollection<E>` Parameters: `o` - element to be removed from this deque, if present Returns: `true` if this deque changed as a result of the call

### method:size() [NONE]
### size public int size() Returns the number of elements in this deque. Specified by: `size` in interface `BlockingDeque<E>` Specified by: `size` in interface `Collection<E>` Specified by: `size` in interface `Deque<E>` Returns: the number of elements in this deque

### method:contains(java.lang.Object) [NONE]
### contains public boolean contains (Object o) Returns `true` if this deque contains the specified element. More formally, returns `true` if and only if this deque contains at least one element `e` such that `o.equals(e)`. Specified by: `contains` in interface `BlockingDeque<E>` Specified by: `contains` in interface `BlockingQueue<E>` Specified by: `contains` in interface `Collection<E>` Specified by: `contains` in interface `Deque<E>` Overrides: `contains` in class `AbstractCollection<E>` Parameters: `o` - object to be checked for containment in this deque Returns: `true` if this deque contains the specified element

### method:addAll(java.util.Collection) [NONE]
### addAll public boolean addAll (Collection<? extends E> c) Appends all of the elements in the specified collection to the end of this deque, in the order that they are returned by the specified collection's iterator. Attempts to `addAll` of a deque to itself result in `IllegalArgumentException`. Specified by: `addAll` in interface `Collection<E>` Specified by: `addAll` in interface `Deque<E>` Overrides: `addAll` in class `AbstractQueue<E>` Parameters: `c` - the elements to be inserted into this deque Returns: `true` if this deque changed as a result of the call Throws: `NullPointerException` - if the specified collection or any of its elements are null `IllegalArgumentException` - if the collection is this deque `IllegalStateException` - if this deque is full See Also: `add(Object)`

### method:toArray() [NONE]
- ### toArray public Object[] toArray() Returns an array containing all of the elements in this deque, in proper sequence (from first to last element). The returned array will be "safe" in that no references to it are maintained by this deque. (In other words, this method must allocate a new array). The caller is thus free to modify the returned array. This method acts as bridge between array-based and collection-based APIs. Specified by: `toArray` in interface `Collection<E>` Overrides: `toArray` in class `AbstractCollection<E>` Returns: an array containing all of the elements in this deque ### toArray public <T> T[] toArray (T[] a) Returns an array containing all of the elements in this deque, in proper sequence; the runtime type of the returned array is that of the specified array. If the deque fits in the specified array, it is returned therein. Otherwise, a new array is allocated with the runtime type of the specified array and the size of this deque. If this deque fits in the specified array with room to spare (i.e., the array has more elements than this deque), the element in the array immediately following the end of the deque is set to `null`. Like the `toArray()` method, this method acts as bridge between array-based and collection-based APIs. Further, this method allows precise control over the runtime type of the output array, and may, under certain circumstances, be used to save allocation costs. Suppose `x` is a deque known to contain only strings. The following code can be used to dump the deque into a newly allocated array of `String`:
      String[] y = x.toArray(new String[0]);
Note that `toArray(new Object[0])` is identical in function to `toArray()`. Specified by: `toArray` in interface `Collection<E>` Overrides: `toArray` in class `AbstractCollection<E>` Type Parameters: `T` - the component type of the array to contain the collection Parameters: `a` - the array into which the elements of the deque are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purpose Returns: an array containing all of the elements in this deque Throws: `ArrayStoreException` - if the runtime type of the specified array is not a supertype of the runtime type of every element in this deque `NullPointerException` - if the specified array is null

### method:clear() [NONE]
### clear public void clear() Atomically removes all of the elements from this deque. The deque will be empty after this call returns. Specified by: `clear` in interface `Collection<E>` Overrides: `clear` in class `AbstractQueue<E>`

### method:iterator() [NONE]
### iterator public Iterator<E> iterator() Returns an iterator over the elements in this deque in proper sequence. The elements will be returned in order from first (head) to last (tail). The returned iterator is weakly consistent . Specified by: `iterator` in interface `BlockingDeque<E>` Specified by: `iterator` in interface `Collection<E>` Specified by: `iterator` in interface `Deque<E>` Specified by: `iterator` in interface `Iterable<E>` Specified by: `iterator` in class `AbstractCollection<E>` Returns: an iterator over the elements in this deque in proper sequence

### method:descendingIterator() [NONE]
### descendingIterator public Iterator<E> descendingIterator() Returns an iterator over the elements in this deque in reverse sequential order. The elements will be returned in order from last (tail) to first (head). The returned iterator is weakly consistent . Specified by: `descendingIterator` in interface `Deque<E>` Returns: an iterator over the elements in this deque in reverse order

### method:spliterator() [NONE]
### spliterator public Spliterator<E> spliterator() Returns a `Spliterator` over the elements in this deque. The returned spliterator is weakly consistent . The `Spliterator` reports `Spliterator.CONCURRENT`, `Spliterator.ORDERED`, and `Spliterator.NONNULL`. Specified by: `spliterator` in interface `Collection<E>` Specified by: `spliterator` in interface `Iterable<E>` Implementation Note: The `Spliterator` implements `trySplit` to permit limited parallelism. Returns: a `Spliterator` over the elements in this deque Since: 1.8

### method:forEach(java.util.function.Consumer) [NONE]
### forEach public void forEach (Consumer<? super E> action) Description copied from interface: `Iterable` Performs the given action for each element of the `Iterable` until all elements have been processed or the action throws an exception. Actions are performed in the order of iteration, if that order is specified. Exceptions thrown by the action are relayed to the caller. The behavior of this method is unspecified if the action performs side-effects that modify the underlying source of elements, unless an overriding class has specified a concurrent modification policy. Specified by: `forEach` in interface `Iterable<E>` Parameters: `action` - The action to be performed for each element Throws: `NullPointerException` - if the specified action is null

### method:removeIf(java.util.function.Predicate) [NONE]
### removeIf public boolean removeIf (Predicate<? super E> filter) Description copied from interface: `Collection` Removes all of the elements of this collection that satisfy the given predicate. Errors or runtime exceptions thrown during iteration or by the predicate are relayed to the caller. Specified by: `removeIf` in interface `Collection<E>` Parameters: `filter` - a predicate which returns `true` for elements to be removed Returns: `true` if any elements were removed Throws: `NullPointerException` - if the specified filter is null

### method:removeAll(java.util.Collection) [NONE]
### removeAll public boolean removeAll (Collection<?> c) Description copied from class: `AbstractCollection` Removes all of this collection's elements that are also contained in the specified collection (optional operation). After this call returns, this collection will contain no elements in common with the specified collection. Specified by: `removeAll` in interface `Collection<E>` Overrides: `removeAll` in class `AbstractCollection<E>` Parameters: `c` - collection containing elements to be removed from this collection Returns: `true` if this collection changed as a result of the call Throws: `NullPointerException` - if this collection contains one or more null elements and the specified collection does not support null elements (optional), or if the specified collection is null See Also: `AbstractCollection.remove(Object)` `AbstractCollection.contains(Object)`

### method:retainAll(java.util.Collection) [NONE]
### retainAll public boolean retainAll (Collection<?> c) Description copied from class: `AbstractCollection` 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. Specified by: `retainAll` in interface `Collection<E>` Overrides: `retainAll` in class `AbstractCollection<E>` Parameters: `c` - collection containing elements to be retained in this collection Returns: `true` if this collection changed as a result of the call Throws: `NullPointerException` - if this collection contains one or more null elements and the specified collection does not permit null elements (optional), or if the specified collection is null See Also: `AbstractCollection.remove(Object)` `AbstractCollection.contains(Object)`