com.espertech.esper.collection
Class ArrayDequeJDK6Backport<E>

java.lang.Object
  extended by java.util.AbstractCollection<E>
      extended by com.espertech.esper.collection.ArrayDequeJDK6Backport<E>
Type Parameters:
E - the type of elements held in this collection
All Implemented Interfaces:
Serializable, Cloneable, Iterable<E>, Collection<E>

public class ArrayDequeJDK6Backport<E>
extends AbstractCollection<E>
implements Cloneable, Serializable

Backport of the JDK6 ArrayDeque class as from the Sun source distribution of JDK 1.6.0_3.

Faster for adding, removing and iterating over elements when compared to LinkedList. More expensive for toArray() then LinkedList. Slightly more expensive for construction then LinkedList. Resizable-array implementation of the JDK6 Deque interface. Array deques have no capacity restrictions; they grow as necessary to support usage. They are not thread-safe; in the absence of external synchronization, they do not support concurrent access by multiple threads. Null elements are prohibited. This class is likely to be faster than Stack when used as a stack, and faster than LinkedList when used as a queue.

Most ArrayDeque operations run in amortized constant time. Exceptions include remove, removeFirstOccurrence, removeLastOccurrence, contains, iterator.remove(), and the bulk operations, all of which run in linear time.

The iterators returned by this class's iterator method are fail-fast: If the deque is modified at any time after the iterator is created, in any way except through the iterator's own remove method, the iterator will generally throw a ConcurrentModificationException. Thus, in the face of concurrent modification, the iterator fails quickly and cleanly, rather than risking arbitrary, non-deterministic behavior at an undetermined time in the future.

Note that the fail-fast behavior of an iterator cannot be guaranteed as it is, generally speaking, impossible to make any hard guarantees in the presence of unsynchronized concurrent modification. Fail-fast iterators throw ConcurrentModificationException on a best-effort basis. Therefore, it would be wrong to write a program that depended on this exception for its correctness: the fail-fast behavior of iterators should be used only to detect bugs.

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
Author:
Josh Bloch and Doug Lea
See Also:
Serialized Form

Constructor Summary
ArrayDequeJDK6Backport()
          Constructs an empty array deque with an initial capacity sufficient to hold 16 elements.
ArrayDequeJDK6Backport(Collection<? extends E> c)
          Constructs a deque containing the elements of the specified collection, in the order they are returned by the collection's iterator.
ArrayDequeJDK6Backport(int numElements)
          Constructs an empty array deque with an initial capacity sufficient to hold the specified number of elements.
 
Method Summary
 boolean add(E e)
          Inserts the specified element at the end of this deque.
 void addFirst(E e)
          Inserts the specified element at the front of this deque.
 void addLast(E e)
          Inserts the specified element at the end of this deque.
 void clear()
          Removes all of the elements from this deque.
 boolean contains(Object o)
          Returns true if this deque contains the specified element.
 Iterator<E> descendingIterator()
          See equivalent Queue API method.
 E element()
          Retrieves, but does not remove, the head of the queue represented by this deque.
 E getFirst()
          See equivalent Queue API method.
 E getLast()
          See equivalent Queue API method.
 boolean isEmpty()
          Returns true if this deque contains no elements.
 Iterator<E> iterator()
          Returns an iterator over the elements in this deque.
 boolean offer(E e)
          Inserts the specified element at the end of this deque.
 boolean offerFirst(E e)
          Inserts the specified element at the front of this deque.
 boolean offerLast(E e)
          Inserts the specified element at the end of this deque.
 E peek()
          Retrieves, but does not remove, the head of the queue represented by this deque, or returns null if this deque is empty.
 E peekFirst()
          See equivalent Queue API method.
 E peekLast()
          See equivalent Queue API method.
 E poll()
          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.
 E pollFirst()
          See equivalent Queue API method.
 E pollLast()
          See equivalent Queue API method.
 E pop()
          Pops an element from the stack represented by this deque.
 void push(E e)
          Pushes an element onto the stack represented by this deque.
 E remove()
          Retrieves and removes the head of the queue represented by this deque.
 boolean remove(Object o)
          Removes a single instance of the specified element from this deque.
 E removeFirst()
           
 boolean removeFirstOccurrence(Object o)
          Removes the first occurrence of the specified element in this deque (when traversing the deque from head to tail).
 E removeLast()
           
 boolean removeLastOccurrence(Object o)
          Removes the last occurrence of the specified element in this deque (when traversing the deque from head to tail).
 int size()
          Returns the number of elements in this deque.
 Object[] toArray()
          Returns an array containing all of the elements in this deque in proper sequence (from first to last element).
<T> T[]
toArray(T[] a)
          Returns an array containing all of the elements in this deque in proper sequence (from first to last element); the runtime type of the returned array is that of the specified array.
 
Methods inherited from class java.util.AbstractCollection
addAll, containsAll, removeAll, retainAll, toString
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 
Methods inherited from interface java.util.Collection
equals, hashCode
 

Constructor Detail

ArrayDequeJDK6Backport

public ArrayDequeJDK6Backport()
Constructs an empty array deque with an initial capacity sufficient to hold 16 elements.


ArrayDequeJDK6Backport

public ArrayDequeJDK6Backport(int numElements)
Constructs an empty array deque with an initial capacity sufficient to hold the specified number of elements.

Parameters:
numElements - lower bound on initial capacity of the deque

ArrayDequeJDK6Backport

public ArrayDequeJDK6Backport(Collection<? extends E> c)
Constructs a deque containing the elements of the specified collection, in the order they are returned by the collection's iterator. (The first element returned by the collection's iterator becomes the first element, or front of the deque.)

Parameters:
c - the collection whose elements are to be placed into the deque
Throws:
NullPointerException - if the specified collection is null
Method Detail

addFirst

public void addFirst(E e)
Inserts the specified element at the front of this deque.

Parameters:
e - the element to add
Throws:
NullPointerException - if the specified element is null

addLast

public void addLast(E e)
Inserts the specified element at the end of this deque.

This method is equivalent to add(E).

Parameters:
e - the element to add
Throws:
NullPointerException - if the specified element is null

offerFirst

public boolean offerFirst(E e)
Inserts the specified element at the front of this deque.

Parameters:
e - the element to add
Returns:
true (as specified by offerFirst
Throws:
NullPointerException - if the specified element is null

offerLast

public boolean offerLast(E e)
Inserts the specified element at the end of this deque.

Parameters:
e - the element to add
Returns:
true (as specified by offerLast
Throws:
NullPointerException - if the specified element is null

removeFirst

public E removeFirst()
Returns:
first
Throws:
NoSuchElementException - no more elements

removeLast

public E removeLast()
Returns:
last
Throws:
NoSuchElementException - no more elements

pollFirst

public E pollFirst()
See equivalent Queue API method.

Returns:
first or null

pollLast

public E pollLast()
See equivalent Queue API method.

Returns:
last or null

getFirst

public E getFirst()
See equivalent Queue API method.

Returns:
first
Throws:
NoSuchElementException - no more elements

getLast

public E getLast()
See equivalent Queue API method.

Returns:
last
Throws:
NoSuchElementException - no more elements

peekFirst

public E peekFirst()
See equivalent Queue API method.

Returns:
first

peekLast

public E peekLast()
See equivalent Queue API method.

Returns:
last

removeFirstOccurrence

public boolean removeFirstOccurrence(Object o)
Removes the first occurrence of the specified element in this deque (when traversing the deque from head to tail). 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).

Parameters:
o - element to be removed from this deque, if present
Returns:
true if the deque contained the specified element

removeLastOccurrence

public boolean removeLastOccurrence(Object o)
Removes the last occurrence of the specified element in this deque (when traversing the deque from head to tail). 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).

Parameters:
o - element to be removed from this deque, if present
Returns:
true if the deque contained the specified element

add

public boolean add(E e)
Inserts the specified element at the end of this deque.

This method is equivalent to addLast(E).

Specified by:
add in interface Collection<E>
Overrides:
add in class AbstractCollection<E>
Parameters:
e - the element to add
Returns:
true (as specified by Collection.add(E))
Throws:
NullPointerException - if the specified element is null

offer

public boolean offer(E e)
Inserts the specified element at the end of this deque.

This method is equivalent to offerLast(E).

Parameters:
e - the element to add
Returns:
true (as specified by Queue.offer(E))
Throws:
NullPointerException - if the specified element is null

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().

Returns:
the head of the queue represented by this deque
Throws:
NoSuchElementException - no more elements

poll

public E poll()
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 pollFirst().

Returns:
the head of the queue represented by this deque, or null if this deque is empty

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().

Returns:
the head of the queue represented by this deque
Throws:
NoSuchElementException - no more elements

peek

public E peek()
Retrieves, but does not remove, the head of the queue represented by this deque, or returns null if this deque is empty.

This method is equivalent to peekFirst().

Returns:
the head of the queue represented by this deque, or null if this deque is empty

push

public void push(E e)
Pushes an element onto the stack represented by this deque. In other words, inserts the element at the front of this deque.

This method is equivalent to addFirst(E).

Parameters:
e - the element to push
Throws:
NullPointerException - if the specified element is null

pop

public E pop()
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 removeFirst().

Returns:
the element at the front of this deque (which is the top of the stack represented by this deque)
Throws:
NoSuchElementException - no more elements

size

public int size()
Returns the number of elements in this deque.

Specified by:
size in interface Collection<E>
Specified by:
size in class AbstractCollection<E>
Returns:
the number of elements in this deque

isEmpty

public boolean isEmpty()
Returns true if this deque contains no elements.

Specified by:
isEmpty in interface Collection<E>
Overrides:
isEmpty in class AbstractCollection<E>
Returns:
true if this deque contains no elements

iterator

public Iterator<E> iterator()
Returns an iterator over the elements in this deque. The elements will be ordered from first (head) to last (tail). This is the same order that elements would be dequeued (via successive calls to remove() or popped (via successive calls to pop()).

Specified by:
iterator in interface Iterable<E>
Specified by:
iterator in interface Collection<E>
Specified by:
iterator in class AbstractCollection<E>
Returns:
an iterator over the elements in this deque

descendingIterator

public Iterator<E> descendingIterator()
See equivalent Queue API method.

Returns:
iterator

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 Collection<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

remove

public boolean remove(Object o)
Removes a single instance 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(java.lang.Object).

Specified by:
remove in interface Collection<E>
Overrides:
remove in class AbstractCollection<E>
Parameters:
o - element to be removed from this deque, if present
Returns:
true if this deque contained the specified element

clear

public void clear()
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 AbstractCollection<E>

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 (from first to last element); 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>
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

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