src/jsr166x/Deque.java

/*
 * Written by Doug Lea and Josh Bloch with assistance from members of
 * JCP JSR-166 Expert Group and released to the public domain, as explained
 * at http://creativecommons.org/licenses/publicdomain
 */

package jsr166x;     // XXX This belongs in java.util!!! XXX
import java.util.*;    // XXX This import goes away        XXX

/**
 * A linear collection that supports element insertion and removal at
 * both ends.  The name <i>deque</i> is short for "double ended queue"
 * and is usually pronounced "deck".  Most <tt>Deque</tt>
 * implementations place no fixed limits on the number of elements
 * they may contain, but this interface supports capacity-restricted
 * deques as well as those with no fixed size limit.
 *
 * <p>This interface defines methods to access the elements at both
 * ends of the deque.  Methods are provided to insert, remove, and
 * examine the element.  Each of these methods exists in two forms:
 * one throws an exception if the operation fails, the other returns a
 * special value (either <tt>null</tt> or <tt>false</tt>, depending on
 * the operation).  The latter form of the insert operation is
 * designed specifically for use with capacity-restricted
 * <tt>Deque</tt> implementations; in most implementations, insert
 * operations cannot fail.
 *
 * <p>The twelve methods described above are are summarized in the
 * follwoing table:<p>
 *
 * <table BORDER CELLPADDING=3 CELLSPACING=1>
 *  <tr>
 *    <td></td>
 *    <td ALIGN=CENTER COLSPAN = 2> <b>First Element (Head)</b></td>
 *    <td ALIGN=CENTER COLSPAN = 2> <b>Last Element (Tail)</b></td>
 *  </tr>
 *  <tr>
 *    <td></td>
 *    <td ALIGN=CENTER><em>Throws exception</em></td>
 *    <td ALIGN=CENTER><em>Returns special value</em></td>
 *    <td ALIGN=CENTER><em>Throws exception</em></td>
 *    <td ALIGN=CENTER><em>Returns special value</em></td>
 *  </tr>
 *  <tr>
 *    <td><b>Insert</b></td>
 *    <td>{@link #addFirst addFirst(e)}</td>
 *    <td>{@link #offerFirst offerFirst(e)}</td>
 *    <td>{@link #addLast addLast(e)}</td>
 *    <td>{@link #offerLast offerLast(e)}</td>
 *  </tr>
 *  <tr>
 *    <td><b>Remove</b></td>
 *    <td>{@link #removeFirst removeFirst()}</td>
 *    <td>{@link #pollFirst pollFirst()}</td>
 *    <td>{@link #removeLast removeLast()}</td>
 *    <td>{@link #pollLast pollLast()}</td>
 *  </tr>
 *  <tr>
 *    <td><b>Examine</b></td>
 *    <td>{@link #getFirst getFirst()}</td>
 *    <td>{@link #peekFirst peekFirst()}</td>
 *    <td>{@link #getLast getLast()}</td>
 *    <td>{@link #peekLast peekLast()}</td>
 *  </tr>
 * </table>
 *
 * <p>This interface extends the {@link Queue} interface.  When a deque is
 * used as a queue, FIFO (First-In-First-Out) behavior results.  Elements are
 * added to the end of the deque and removed from the beginning.  The methods
 * inherited from the <tt>Queue</tt> interface are precisely equivalent to
 * <tt>Deque</tt> methods as indicated in the following table:<p>
 *
 * <table BORDER CELLPADDING=3 CELLSPACING=1>
 *  <tr>
 *    <td ALIGN=CENTER> <b><tt>Queue</tt> Method</b></td>
 *    <td ALIGN=CENTER> <b>Equivalent <tt>Deque</tt> Method</b></td>
 *  </tr>
 *  <tr>
 *   <tr>
 *    <td>{@link java.util.Queue#offer offer(e)}</td>
 *    <td>{@link #offerLast offerLast(e)}</td>
 *   </tr>
 *   <tr>
 *    <td>{@link java.util.Queue#add add(e)}</td>
 *    <td>{@link #addLast addLast(e)}</td>
 *   </tr>
 *   <tr>
 *    <td>{@link java.util.Queue#poll poll()}</td>
 *    <td>{@link #pollFirst pollFirst()}</td>
 *   </tr>
 *   <tr>
 *    <td>{@link java.util.Queue#remove remove()}</td>
 *    <td>{@link #removeFirst removeFirst()}</td>
 *   </tr>
 *   <tr>
 *    <td>{@link java.util.Queue#peek peek()}</td>
 *    <td>{@link #peek peekFirst()}</td>
 *   </tr>
 *   <tr>
 *    <td>{@link java.util.Queue#element element()}</td>
 *    <td>{@link #getFirst getFirst()}</td>
 *   </tr>
 * </table>
 *
 * <p>Deques can also be used as LIFO (Last-In-First-Out) stacks.  This
 * interface should be used in preference to the legacy {@link Stack} class.
 * When a dequeue is used as a stack, elements are pushed and popped from the
 * beginning of the deque.  Stack methods are precisely equivalent to
 * <tt>Deque</tt> methods as indicated in the table below:<p>
 *
 * <table BORDER CELLPADDING=3 CELLSPACING=1>
 *  <tr>
 *    <td ALIGN=CENTER> <b>Stack Method</b></td>
 *    <td ALIGN=CENTER> <b>Equivalent <tt>Deque</tt> Method</b></td>
 *  </tr>
 *  <tr>
 *   <tr>
 *    <td>{@link #push push(e)}</td>
 *    <td>{@link #addFirst addFirst(e)}</td>
 *   </tr>
 *   <tr>
 *    <td>{@link #pop pop()}</td>
 *    <td>{@link #removeFirst removeFirst()}</td>
 *   </tr>
 *   <tr>
 *    <td>{@link #peek peek()}</td>
 *    <td>{@link #peekFirst peekFirst()}</td>
 *   </tr>
 * </table>
 *
 * <p>Note that the {@link #peek peek} method works equally well when
 * a deque is used as a queue or a stack; in either case, elements are
 * drawn from the beginning of the deque.
 *
 * <p>This interface provides two methods to remove interior
 * elements, {@link #removeFirstOccurrence removeFirstOccurrence} and
 * {@link #removeLastOccurrence removeLastOccurrence}.  Unlike the
 * {@link List} interface, this interface does not provide support for
 * indexed access to elements.
 *
 * <p>While <tt>Deque</tt> implementations are not strictly required
 * to prohibit the insertion of null elements, they are strongly
 * encouraged to do so.  Users of any <tt>Deque</tt> implementations
 * that do allow null elements are strongly encouraged <i>not</i> to
 * take advantage of the ability to insert nulls.  This is so because
 * <tt>null</tt> is used as a special return value by various methods
 * to indicated that the deque is empty.
 *
 * <p><tt>Deque</tt> implementations generally do not define
 * element-based versions of the <tt>equals</tt> and <tt>hashCode</tt>
 * methods, but instead inherit the identity-based versions from class
 * <tt>Object</tt>.
 *
 * <p>This interface is a member of the <a
 * href="{@docRoot}/../guide/collections/index.html"> Java Collections
 * Framework</a>.
 *
 * @author Doug Lea
 * @author Josh Bloch
 * @since  1.6
 * @param <E> the type of elements held in this collection
 */
public interface Deque<E> extends Queue<E> {
    /**
     * Inserts the specified element to the front this deque unless it would
     * violate capacity restrictions.  When using a capacity-restricted deque,
     * this method is generally preferable to method <tt>addFirst</tt>, which
     * can fail to insert an element only by throwing an exception.
     *
     * @param e the element to insert
     * @return <tt>true</tt> if it was possible to insert the element,
     *     else <tt>false</tt>
     * @throws NullPointerException if <tt>e</tt> is null and this
     *     deque does not permit null elements
     */
    boolean offerFirst(E e);

    /**
     * Inserts the specified element to the end of this deque unless it would
     * violate capacity restrictions.  When using a capacity-restricted deque,
     * this method is generally preferable to method <tt>addLast</tt> which
     * can fail to insert an element only by throwing an exception.
     *
     * @param e the element to insert
     * @return <tt>true</tt> if it was possible to insert the element,
     *     else <tt>false</tt>
     * @throws NullPointerException if <tt>e</tt> is null and this
     *     deque does not permit null elements
     */
    boolean offerLast(E e);

    /**
     * Inserts the specified element to the front of this deque unless it
     * would violate capacity restrictions.
     *
     * @param e the element to insert
     * @throws IllegalStateException if it was not possible to insert
     *    the element due to capacity restrictions
     * @throws NullPointerException if <tt>e</tt> is null and this
     *     deque does not permit null elements
     */
    void addFirst(E e);

    /**
     * Inserts the specified element to the end of this deque unless it would
     * violate capacity restrictions.
     *
     * @param e the element to insert
     * @throws IllegalStateException if it was not possible to insert
     *    the element due to capacity restrictions
     * @throws NullPointerException if <tt>e</tt> is null and this
     *     deque does not permit null elements
     */
    void addLast(E e);

    /**
     * Retrieves and removes the first element of this deque, or
     * <tt>null</tt> if this deque is empty.
     *
     * @return the first element of this deque, or <tt>null</tt> if
     *     this deque is empty
     */
    E pollFirst();

    /**
     * Retrieves and removes the last element of this deque, or
     * <tt>null</tt> if this deque is empty.
     *
     * @return the last element of this deque, or <tt>null</tt> if
     *     this deque is empty
     */
    E pollLast();

    /**
     * Removes and returns the first element of this deque.  This method
     * differs from the <tt>pollFirst</tt> method only in that it throws an
     * exception if this deque is empty.
     *
     * @return the first element of this deque
     * @throws NoSuchElementException if this deque is empty
     */
    E removeFirst();

    /**
     * Retrieves and removes the last element of this deque.  This method
     * differs from the <tt>pollLast</tt> method only in that it throws an
     * exception if this deque is empty.
     *
     * @return the last element of this deque
     * @throws NoSuchElementException if this deque is empty
     */
    E removeLast();

    /**
     * Retrieves, but does not remove, the first element of this deque,
     * returning <tt>null</tt> if this deque is empty.
     *
     * @return the first element of this deque, or <tt>null</tt> if
     *     this deque is empty
     */
    E peekFirst();

    /**
     * Retrieves, but does not remove, the last element of this deque,
     * returning <tt>null</tt> if this deque is empty.
     *
     * @return the last element of this deque, or <tt>null</tt> if this deque
     *     is empty
     */
    E peekLast();

    /**
     * Retrieves, but does not remove, the first element of this
     * deque.  This method differs from the <tt>peek</tt> method only
     * in that it throws an exception if this deque is empty.
     *
     * @return the first element of this deque
     * @throws NoSuchElementException if this deque is empty
     */
    E getFirst();

    /**
     * Retrieves, but does not remove, the last element of this
     * deque.  This method differs from the <tt>peek</tt> method only
     * in that it throws an exception if this deque is empty.
     *
     * @return the last element of this deque
     * @throws NoSuchElementException if this deque is empty
     */
    E getLast();

    /**
     * Removes the first occurrence of the specified element in this
     * deque.  If the deque does not contain the element, it is
     * unchanged.  More formally, removes the first element <tt>e</tt>
     * such that <tt>(o==null ? e==null : o.equals(e))</tt> (if
     * such an element exists).
     *
     * @param e element to be removed from this deque, if present
     * @return <tt>true</tt> if the deque contained the specified element
     * @throws NullPointerException if the specified element is <tt>null</tt>
     */
    boolean removeFirstOccurrence(Object e);

    /**
     * Removes the last occurrence of the specified element in this
     * deque.  If the deque does not contain the element, it is
     * unchanged.  More formally, removes the last element <tt>e</tt>
     * such that <tt>(o==null ? e==null : o.equals(e))</tt> (if
     * such an element exists).
     *
     * @param e element to be removed from this deque, if present
     * @return <tt>true</tt> if the deque contained the specified element
     * @throws NullPointerException if the specified element is <tt>null</tt>
     */
    boolean removeLastOccurrence(Object e);


    // *** Queue methods ***

    /**
     * Inserts the specified element into the queue represented by this deque
     * unless it would violate capacity restrictions.  In other words, inserts
     * the specified element to the end of this deque.  When using a
     * capacity-restricted deque, this method is generally preferable to the
     * {@link #add} method, which can fail to insert an element only by
     * throwing an exception.
     *
     * <p>This method is equivalent to {@link #offerLast}.
     *
     * @param e the element to insert
     * @return <tt>true</tt> if it was possible to insert the element,
     *     else <tt>false</tt>
     * @throws NullPointerException if <tt>e</tt> is null and this
     *     deque does not permit null elements
     */
    boolean offer(E e);

    /**
     * Inserts the specified element into the queue represented by this
     * deque unless it would violate capacity restrictions.  In other words,
     * inserts the specified element as the last element of this deque.
     *
     * <p>This method is equivalent to {@link #addLast}.
     *
     * @param e the element to insert
     * @return <tt>true</tt> (as per the spec for {@link Collection#add})
     * @throws IllegalStateException if it was not possible to insert
     *    the element due to capacity restrictions
     * @throws NullPointerException if <tt>e</tt> is null and this
     *     deque does not permit null elements
     */
    boolean add(E e);

    /**
     * Retrieves and removes the head of the queue represented by
     * this deque, or <tt>null</tt> if this deque is empty.  In other words,
     * retrieves and removes the first element of this deque, or <tt>null</tt>
     * if this deque is empty.
     *
     * <p>This method is equivalent to {@link #pollFirst()}.
     *
     * @return the first element of this deque, or <tt>null</tt> if
     *     this deque is empty
     */
    E poll();

    /**
     * Retrieves and removes the head of the queue represented by this deque.
     * This method differs from the <tt>poll</tt> method only in that it
     * throws an exception if this deque is empty.
     *
     * <p>This method is equivalent to {@link #removeFirst()}.
     *
     * @return the head of the queue represented by this deque
     * @throws NoSuchElementException if this deque is empty
     */
    E remove();

    /**
     * Retrieves, but does not remove, the head of the queue represented by
     * this deque, returning <tt>null</tt> if this deque is empty.
     *
     * <p>This method is equivalent to {@link #peekFirst()}
     *
     * @return the head of the queue represented by this deque, or
     *     <tt>null</tt> if this deque is empty
     */
    E peek();

    /**
     * Retrieves, but does not remove, the head of the queue represented by
     * this deque.  This method differs from the <tt>peek</tt> method only in
     * that it throws an exception if this deque is empty.
     *
     * <p>This method is equivalent to {@link #getFirst()}
     *
     * @return the head of the queue represented by this deque
     * @throws NoSuchElementException if this deque is empty
     */
    E element();


    // *** Stack methods ***

    /**
     * Pushes an element onto the stack represented by this deque.  In other
     * words, inserts the element to the front this deque unless it would
     * violate capacity restrictions.
     *
     * <p>This method is equivalent to {@link #addFirst}.
     *
     * @throws IllegalStateException if it was not possible to insert
     *    the element due to capacity restrictions
     * @throws NullPointerException if <tt>e</tt> is null and this
     *     deque does not permit null elements
     */
    void push(E e);

    /**
     * Pops an element from the stack represented by this deque.  In other
     * words, removes and returns the first element of this deque.
     *
     * <p>This method is equivalent to {@link #removeFirst()}.
     *
     * @return 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
     */
    E pop();


    // *** Collection Method ***

    /**
     * Returns an iterator over the elements in this deque.  The elements
     * will be ordered from first (head) to last (tail).
     *
     * @return an <tt>Iterator</tt> over the elements in this deque
     */
    Iterator<E> iterator();
}
Revision:	1.8
Committed:	Tue Sep 7 06:03:19 2010 UTC (13 years, 8 months ago) by jsr166
Branch:	MAIN
Changes since 1.7:	+1 -1 lines
Log Message:	double trouble
#	User	Rev	Content
1	dl	1.1	/*
2	dl	1.3	* Written by Doug Lea and Josh Bloch with assistance from members of
3			* JCP JSR-166 Expert Group and released to the public domain, as explained
4			* at http://creativecommons.org/licenses/publicdomain
5	dl	1.1	*/
6
7	dl	1.3	package jsr166x; // XXX This belongs in java.util!!! XXX
8			import java.util.*; // XXX This import goes away XXX
9	dl	1.1
10			/**
11	dl	1.5	* A linear collection that supports element insertion and removal at
12			* both ends. The name <i>deque</i> is short for "double ended queue"
13			* and is usually pronounced "deck". Most <tt>Deque</tt>
14	dl	1.3	* implementations place no fixed limits on the number of elements
15			* they may contain, but this interface supports capacity-restricted
16			* deques as well as those with no fixed size limit.
17			*
18	dl	1.5	* <p>This interface defines methods to access the elements at both
19			* ends of the deque. Methods are provided to insert, remove, and
20			* examine the element. Each of these methods exists in two forms:
21			* one throws an exception if the operation fails, the other returns a
22			* special value (either <tt>null</tt> or <tt>false</tt>, depending on
23			* the operation). The latter form of the insert operation is
24			* designed specifically for use with capacity-restricted
25			* <tt>Deque</tt> implementations; in most implementations, insert
26			* operations cannot fail.
27	dl	1.3	*
28	jsr166	1.6	* <p>The twelve methods described above are are summarized in the
29	dl	1.3	* follwoing table:<p>
30	jsr166	1.6	*
31	dl	1.3	* <table BORDER CELLPADDING=3 CELLSPACING=1>
32			* <tr>
33			* <td></td>
34			* <td ALIGN=CENTER COLSPAN = 2> <b>First Element (Head)</b></td>
35			* <td ALIGN=CENTER COLSPAN = 2> <b>Last Element (Tail)</b></td>
36			* </tr>
37			* <tr>
38			* <td></td>
39			* <td ALIGN=CENTER><em>Throws exception</em></td>
40			* <td ALIGN=CENTER><em>Returns special value</em></td>
41			* <td ALIGN=CENTER><em>Throws exception</em></td>
42			* <td ALIGN=CENTER><em>Returns special value</em></td>
43			* </tr>
44			* <tr>
45			* <td><b>Insert</b></td>
46			* <td>{@link #addFirst addFirst(e)}</td>
47			* <td>{@link #offerFirst offerFirst(e)}</td>
48			* <td>{@link #addLast addLast(e)}</td>
49			* <td>{@link #offerLast offerLast(e)}</td>
50			* </tr>
51			* <tr>
52			* <td><b>Remove</b></td>
53			* <td>{@link #removeFirst removeFirst()}</td>
54			* <td>{@link #pollFirst pollFirst()}</td>
55			* <td>{@link #removeLast removeLast()}</td>
56			* <td>{@link #pollLast pollLast()}</td>
57			* </tr>
58			* <tr>
59			* <td><b>Examine</b></td>
60	dl	1.4	* <td>{@link #getFirst getFirst()}</td>
61	dl	1.3	* <td>{@link #peekFirst peekFirst()}</td>
62	dl	1.4	* <td>{@link #getLast getLast()}</td>
63	dl	1.3	* <td>{@link #peekLast peekLast()}</td>
64			* </tr>
65			* </table>
66			*
67			* <p>This interface extends the {@link Queue} interface. When a deque is
68			* used as a queue, FIFO (First-In-First-Out) behavior results. Elements are
69			* added to the end of the deque and removed from the beginning. The methods
70			* inherited from the <tt>Queue</tt> interface are precisely equivalent to
71			* <tt>Deque</tt> methods as indicated in the following table:<p>
72			*
73			* <table BORDER CELLPADDING=3 CELLSPACING=1>
74			* <tr>
75			* <td ALIGN=CENTER> <b><tt>Queue</tt> Method</b></td>
76			* <td ALIGN=CENTER> <b>Equivalent <tt>Deque</tt> Method</b></td>
77			* </tr>
78			* <tr>
79			* <tr>
80			* <td>{@link java.util.Queue#offer offer(e)}</td>
81			* <td>{@link #offerLast offerLast(e)}</td>
82			* </tr>
83			* <tr>
84			* <td>{@link java.util.Queue#add add(e)}</td>
85			* <td>{@link #addLast addLast(e)}</td>
86			* </tr>
87			* <tr>
88			* <td>{@link java.util.Queue#poll poll()}</td>
89			* <td>{@link #pollFirst pollFirst()}</td>
90			* </tr>
91			* <tr>
92			* <td>{@link java.util.Queue#remove remove()}</td>
93			* <td>{@link #removeFirst removeFirst()}</td>
94			* </tr>
95			* <tr>
96			* <td>{@link java.util.Queue#peek peek()}</td>
97			* <td>{@link #peek peekFirst()}</td>
98			* </tr>
99			* <tr>
100			* <td>{@link java.util.Queue#element element()}</td>
101	dl	1.4	* <td>{@link #getFirst getFirst()}</td>
102	dl	1.3	* </tr>
103			* </table>
104			*
105			* <p>Deques can also be used as LIFO (Last-In-First-Out) stacks. This
106			* interface should be used in preference to the legacy {@link Stack} class.
107			* When a dequeue is used as a stack, elements are pushed and popped from the
108			* beginning of the deque. Stack methods are precisely equivalent to
109			* <tt>Deque</tt> methods as indicated in the table below:<p>
110			*
111			* <table BORDER CELLPADDING=3 CELLSPACING=1>
112			* <tr>
113			* <td ALIGN=CENTER> <b>Stack Method</b></td>
114			* <td ALIGN=CENTER> <b>Equivalent <tt>Deque</tt> Method</b></td>
115			* </tr>
116			* <tr>
117			* <tr>
118			* <td>{@link #push push(e)}</td>
119			* <td>{@link #addFirst addFirst(e)}</td>
120			* </tr>
121			* <tr>
122			* <td>{@link #pop pop()}</td>
123			* <td>{@link #removeFirst removeFirst()}</td>
124			* </tr>
125			* <tr>
126			* <td>{@link #peek peek()}</td>
127			* <td>{@link #peekFirst peekFirst()}</td>
128			* </tr>
129			* </table>
130	dl	1.5	*
131			* <p>Note that the {@link #peek peek} method works equally well when
132			* a deque is used as a queue or a stack; in either case, elements are
133			* drawn from the beginning of the deque.
134			*
135	jsr166	1.8	* <p>This interface provides two methods to remove interior
136	dl	1.5	* elements, {@link #removeFirstOccurrence removeFirstOccurrence} and
137			* {@link #removeLastOccurrence removeLastOccurrence}. Unlike the
138			* {@link List} interface, this interface does not provide support for
139			* indexed access to elements.
140			*
141			* <p>While <tt>Deque</tt> implementations are not strictly required
142			* to prohibit the insertion of null elements, they are strongly
143			* encouraged to do so. Users of any <tt>Deque</tt> implementations
144			* that do allow null elements are strongly encouraged <i>not</i> to
145			* take advantage of the ability to insert nulls. This is so because
146			* <tt>null</tt> is used as a special return value by various methods
147			* to indicated that the deque is empty.
148	jsr166	1.6	*
149	dl	1.1	* <p><tt>Deque</tt> implementations generally do not define
150	dl	1.3	* element-based versions of the <tt>equals</tt> and <tt>hashCode</tt>
151			* methods, but instead inherit the identity-based versions from class
152			* <tt>Object</tt>.
153	dl	1.1	*
154			* <p>This interface is a member of the <a
155			* href="{@docRoot}/../guide/collections/index.html"> Java Collections
156			* Framework</a>.
157			*
158			* @author Doug Lea
159	dl	1.3	* @author Josh Bloch
160			* @since 1.6
161	dl	1.1	* @param <E> the type of elements held in this collection
162			*/
163	dl	1.3	public interface Deque<E> extends Queue<E> {
164	dl	1.1	/**
165	dl	1.3	* Inserts the specified element to the front this deque unless it would
166			* violate capacity restrictions. When using a capacity-restricted deque,
167			* this method is generally preferable to method <tt>addFirst</tt>, which
168			* can fail to insert an element only by throwing an exception.
169	dl	1.1	*
170	dl	1.3	* @param e the element to insert
171			* @return <tt>true</tt> if it was possible to insert the element,
172			* else <tt>false</tt>
173			* @throws NullPointerException if <tt>e</tt> is null and this
174			* deque does not permit null elements
175	dl	1.1	*/
176	dl	1.3	boolean offerFirst(E e);
177	dl	1.1
178			/**
179	dl	1.3	* Inserts the specified element to the end of this deque unless it would
180			* violate capacity restrictions. When using a capacity-restricted deque,
181			* this method is generally preferable to method <tt>addLast</tt> which
182			* can fail to insert an element only by throwing an exception.
183	dl	1.1	*
184	dl	1.3	* @param e the element to insert
185			* @return <tt>true</tt> if it was possible to insert the element,
186			* else <tt>false</tt>
187			* @throws NullPointerException if <tt>e</tt> is null and this
188			* deque does not permit null elements
189	dl	1.1	*/
190	dl	1.3	boolean offerLast(E e);
191	dl	1.1
192			/**
193	dl	1.3	* Inserts the specified element to the front of this deque unless it
194			* would violate capacity restrictions.
195	dl	1.1	*
196	dl	1.3	* @param e the element to insert
197			* @throws IllegalStateException if it was not possible to insert
198			* the element due to capacity restrictions
199			* @throws NullPointerException if <tt>e</tt> is null and this
200			* deque does not permit null elements
201	dl	1.1	*/
202	dl	1.3	void addFirst(E e);
203	dl	1.1
204			/**
205	dl	1.3	* Inserts the specified element to the end of this deque unless it would
206			* violate capacity restrictions.
207	dl	1.1	*
208	dl	1.3	* @param e the element to insert
209			* @throws IllegalStateException if it was not possible to insert
210			* the element due to capacity restrictions
211			* @throws NullPointerException if <tt>e</tt> is null and this
212			* deque does not permit null elements
213	dl	1.1	*/
214	dl	1.3	void addLast(E e);
215	dl	1.1
216			/**
217			* Retrieves and removes the first element of this deque, or
218			* <tt>null</tt> if this deque is empty.
219			*
220			* @return the first element of this deque, or <tt>null</tt> if
221	dl	1.3	* this deque is empty
222	dl	1.1	*/
223			E pollFirst();
224
225			/**
226			* Retrieves and removes the last element of this deque, or
227			* <tt>null</tt> if this deque is empty.
228			*
229			* @return the last element of this deque, or <tt>null</tt> if
230	dl	1.3	* this deque is empty
231	dl	1.1	*/
232			E pollLast();
233
234			/**
235	dl	1.3	* Removes and returns the first element of this deque. This method
236			* differs from the <tt>pollFirst</tt> method only in that it throws an
237	dl	1.1	* exception if this deque is empty.
238			*
239	dl	1.3	* @return the first element of this deque
240			* @throws NoSuchElementException if this deque is empty
241	dl	1.1	*/
242			E removeFirst();
243
244			/**
245			* Retrieves and removes the last element of this deque. This method
246	dl	1.3	* differs from the <tt>pollLast</tt> method only in that it throws an
247	dl	1.1	* exception if this deque is empty.
248			*
249	dl	1.3	* @return the last element of this deque
250			* @throws NoSuchElementException if this deque is empty
251	dl	1.1	*/
252			E removeLast();
253
254			/**
255			* Retrieves, but does not remove, the first element of this deque,
256			* returning <tt>null</tt> if this deque is empty.
257			*
258			* @return the first element of this deque, or <tt>null</tt> if
259	dl	1.3	* this deque is empty
260	dl	1.1	*/
261			E peekFirst();
262
263			/**
264			* Retrieves, but does not remove, the last element of this deque,
265			* returning <tt>null</tt> if this deque is empty.
266			*
267			* @return the last element of this deque, or <tt>null</tt> if this deque
268	dl	1.3	* is empty
269	dl	1.1	*/
270			E peekLast();
271
272			/**
273			* Retrieves, but does not remove, the first element of this
274			* deque. This method differs from the <tt>peek</tt> method only
275			* in that it throws an exception if this deque is empty.
276			*
277	dl	1.3	* @return the first element of this deque
278			* @throws NoSuchElementException if this deque is empty
279	dl	1.1	*/
280	dl	1.4	E getFirst();
281	dl	1.1
282			/**
283			* Retrieves, but does not remove, the last element of this
284			* deque. This method differs from the <tt>peek</tt> method only
285			* in that it throws an exception if this deque is empty.
286			*
287	dl	1.3	* @return the last element of this deque
288			* @throws NoSuchElementException if this deque is empty
289	dl	1.1	*/
290	dl	1.4	E getLast();
291	dl	1.1
292			/**
293			* Removes the first occurrence of the specified element in this
294			* deque. If the deque does not contain the element, it is
295			* unchanged. More formally, removes the first element <tt>e</tt>
296			* such that <tt>(o==null ? e==null : o.equals(e))</tt> (if
297			* such an element exists).
298			*
299	dl	1.3	* @param e element to be removed from this deque, if present
300			* @return <tt>true</tt> if the deque contained the specified element
301	dl	1.1	* @throws NullPointerException if the specified element is <tt>null</tt>
302			*/
303	dl	1.3	boolean removeFirstOccurrence(Object e);
304	dl	1.1
305			/**
306			* Removes the last occurrence of the specified element in this
307			* deque. If the deque does not contain the element, it is
308			* unchanged. More formally, removes the last element <tt>e</tt>
309			* such that <tt>(o==null ? e==null : o.equals(e))</tt> (if
310			* such an element exists).
311			*
312	dl	1.3	* @param e element to be removed from this deque, if present
313			* @return <tt>true</tt> if the deque contained the specified element
314	dl	1.1	* @throws NullPointerException if the specified element is <tt>null</tt>
315			*/
316	dl	1.3	boolean removeLastOccurrence(Object e);
317
318
319			// * Queue methods *
320	dl	1.1
321			/**
322	dl	1.3	* Inserts the specified element into the queue represented by this deque
323			* unless it would violate capacity restrictions. In other words, inserts
324			* the specified element to the end of this deque. When using a
325			* capacity-restricted deque, this method is generally preferable to the
326			* {@link #add} method, which can fail to insert an element only by
327			* throwing an exception.
328			*
329			* <p>This method is equivalent to {@link #offerLast}.
330			*
331			* @param e the element to insert
332			* @return <tt>true</tt> if it was possible to insert the element,
333			* else <tt>false</tt>
334			* @throws NullPointerException if <tt>e</tt> is null and this
335			* deque does not permit null elements
336	dl	1.1	*/
337	dl	1.3	boolean offer(E e);
338	dl	1.1
339			/**
340	dl	1.3	* Inserts the specified element into the queue represented by this
341			* deque unless it would violate capacity restrictions. In other words,
342	jsr166	1.6	* inserts the specified element as the last element of this deque.
343	dl	1.3	*
344			* <p>This method is equivalent to {@link #addLast}.
345			*
346			* @param e the element to insert
347			* @return <tt>true</tt> (as per the spec for {@link Collection#add})
348			* @throws IllegalStateException if it was not possible to insert
349			* the element due to capacity restrictions
350			* @throws NullPointerException if <tt>e</tt> is null and this
351			* deque does not permit null elements
352			*/
353			boolean add(E e);
354
355			/**
356			* Retrieves and removes the head of the queue represented by
357			* this deque, or <tt>null</tt> if this deque is empty. In other words,
358			* retrieves and removes the first element of this deque, or <tt>null</tt>
359			* if this deque is empty.
360			*
361			* <p>This method is equivalent to {@link #pollFirst()}.
362			*
363			* @return the first element of this deque, or <tt>null</tt> if
364			* this deque is empty
365			*/
366			E poll();
367
368			/**
369			* Retrieves and removes the head of the queue represented by this deque.
370			* This method differs from the <tt>poll</tt> method only in that it
371			* throws an exception if this deque is empty.
372			*
373			* <p>This method is equivalent to {@link #removeFirst()}.
374			*
375			* @return the head of the queue represented by this deque
376			* @throws NoSuchElementException if this deque is empty
377	dl	1.1	*/
378	dl	1.3	E remove();
379	dl	1.1
380	dl	1.3	/**
381			* Retrieves, but does not remove, the head of the queue represented by
382			* this deque, returning <tt>null</tt> if this deque is empty.
383			*
384			* <p>This method is equivalent to {@link #peekFirst()}
385			*
386			* @return the head of the queue represented by this deque, or
387			* <tt>null</tt> if this deque is empty
388			*/
389			E peek();
390
391			/**
392			* Retrieves, but does not remove, the head of the queue represented by
393			* this deque. This method differs from the <tt>peek</tt> method only in
394			* that it throws an exception if this deque is empty.
395			*
396	dl	1.4	* <p>This method is equivalent to {@link #getFirst()}
397	dl	1.3	*
398			* @return the head of the queue represented by this deque
399			* @throws NoSuchElementException if this deque is empty
400			*/
401			E element();
402
403
404			// * Stack methods *
405
406			/**
407			* Pushes an element onto the stack represented by this deque. In other
408			* words, inserts the element to the front this deque unless it would
409			* violate capacity restrictions.
410			*
411			* <p>This method is equivalent to {@link #addFirst}.
412			*
413			* @throws IllegalStateException if it was not possible to insert
414			* the element due to capacity restrictions
415			* @throws NullPointerException if <tt>e</tt> is null and this
416			* deque does not permit null elements
417			*/
418			void push(E e);
419
420			/**
421			* Pops an element from the stack represented by this deque. In other
422	jsr166	1.7	* words, removes and returns the first element of this deque.
423	dl	1.3	*
424			* <p>This method is equivalent to {@link #removeFirst()}.
425			*
426			* @return the element at the front of this deque (which is the top
427			* of the stack represented by this deque)
428			* @throws NoSuchElementException if this deque is empty
429			*/
430			E pop();
431
432
433			// * Collection Method *
434
435			/**
436			* Returns an iterator over the elements in this deque. The elements
437			* will be ordered from first (head) to last (tail).
438	jsr166	1.6	*
439	dl	1.3	* @return an <tt>Iterator</tt> over the elements in this deque
440			*/
441			Iterator<E> iterator();
442	dl	1.1	}