jaroslav@597: /* jaroslav@597: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. jaroslav@597: * jaroslav@597: * This code is free software; you can redistribute it and/or modify it jaroslav@597: * under the terms of the GNU General Public License version 2 only, as jaroslav@597: * published by the Free Software Foundation. Oracle designates this jaroslav@597: * particular file as subject to the "Classpath" exception as provided jaroslav@597: * by Oracle in the LICENSE file that accompanied this code. jaroslav@597: * jaroslav@597: * This code is distributed in the hope that it will be useful, but WITHOUT jaroslav@597: * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or jaroslav@597: * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License jaroslav@597: * version 2 for more details (a copy is included in the LICENSE file that jaroslav@597: * accompanied this code). jaroslav@597: * jaroslav@597: * You should have received a copy of the GNU General Public License version jaroslav@597: * 2 along with this work; if not, write to the Free Software Foundation, jaroslav@597: * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. jaroslav@597: * jaroslav@597: * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA jaroslav@597: * or visit www.oracle.com if you need additional information or have any jaroslav@597: * questions. jaroslav@597: */ jaroslav@597: jaroslav@597: /* jaroslav@597: * This file is available under and governed by the GNU General Public jaroslav@597: * License version 2 only, as published by the Free Software Foundation. jaroslav@597: * However, the following notice accompanied the original version of this jaroslav@597: * file: jaroslav@597: * jaroslav@597: * Written by Doug Lea and Josh Bloch with assistance from members of jaroslav@597: * JCP JSR-166 Expert Group and released to the public domain, as explained jaroslav@597: * at http://creativecommons.org/publicdomain/zero/1.0/ jaroslav@597: */ jaroslav@597: jaroslav@597: package java.util; jaroslav@597: jaroslav@597: /** jaroslav@597: * A linear collection that supports element insertion and removal at jaroslav@597: * both ends. The name deque is short for "double ended queue" jaroslav@597: * and is usually pronounced "deck". Most Deque jaroslav@597: * implementations place no fixed limits on the number of elements jaroslav@597: * they may contain, but this interface supports capacity-restricted jaroslav@597: * deques as well as those with no fixed size limit. jaroslav@597: * jaroslav@597: *

This interface defines methods to access the elements at both jaroslav@597: * ends of the deque. Methods are provided to insert, remove, and jaroslav@597: * examine the element. Each of these methods exists in two forms: jaroslav@597: * one throws an exception if the operation fails, the other returns a jaroslav@597: * special value (either null or false, depending on jaroslav@597: * the operation). The latter form of the insert operation is jaroslav@597: * designed specifically for use with capacity-restricted jaroslav@597: * Deque implementations; in most implementations, insert jaroslav@597: * operations cannot fail. jaroslav@597: * jaroslav@597: *

The twelve methods described above are summarized in the jaroslav@597: * following table: jaroslav@597: * jaroslav@597: *

jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: *
First Element (Head) Last Element (Tail)
Throws exceptionSpecial valueThrows exceptionSpecial value
Insert{@link #addFirst addFirst(e)}{@link #offerFirst offerFirst(e)}{@link #addLast addLast(e)}{@link #offerLast offerLast(e)}
Remove{@link #removeFirst removeFirst()}{@link #pollFirst pollFirst()}{@link #removeLast removeLast()}{@link #pollLast pollLast()}
Examine{@link #getFirst getFirst()}{@link #peekFirst peekFirst()}{@link #getLast getLast()}{@link #peekLast peekLast()}
jaroslav@597: * jaroslav@597: *

This interface extends the {@link Queue} interface. When a deque is jaroslav@597: * used as a queue, FIFO (First-In-First-Out) behavior results. Elements are jaroslav@597: * added at the end of the deque and removed from the beginning. The methods jaroslav@597: * inherited from the Queue interface are precisely equivalent to jaroslav@597: * Deque methods as indicated in the following table: jaroslav@597: * jaroslav@597: *

jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: *
Queue Method Equivalent Deque Method
{@link java.util.Queue#add add(e)}{@link #addLast addLast(e)}
{@link java.util.Queue#offer offer(e)}{@link #offerLast offerLast(e)}
{@link java.util.Queue#remove remove()}{@link #removeFirst removeFirst()}
{@link java.util.Queue#poll poll()}{@link #pollFirst pollFirst()}
{@link java.util.Queue#element element()}{@link #getFirst getFirst()}
{@link java.util.Queue#peek peek()}{@link #peek peekFirst()}
jaroslav@597: * jaroslav@597: *

Deques can also be used as LIFO (Last-In-First-Out) stacks. This jaroslav@597: * interface should be used in preference to the legacy {@link Stack} class. jaroslav@597: * When a deque is used as a stack, elements are pushed and popped from the jaroslav@597: * beginning of the deque. Stack methods are precisely equivalent to jaroslav@597: * Deque methods as indicated in the table below: jaroslav@597: * jaroslav@597: *

jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: * jaroslav@597: *
Stack Method Equivalent Deque Method
{@link #push push(e)}{@link #addFirst addFirst(e)}
{@link #pop pop()}{@link #removeFirst removeFirst()}
{@link #peek peek()}{@link #peekFirst peekFirst()}
jaroslav@597: * jaroslav@597: *

Note that the {@link #peek peek} method works equally well when jaroslav@597: * a deque is used as a queue or a stack; in either case, elements are jaroslav@597: * drawn from the beginning of the deque. jaroslav@597: * jaroslav@597: *

This interface provides two methods to remove interior jaroslav@597: * elements, {@link #removeFirstOccurrence removeFirstOccurrence} and jaroslav@597: * {@link #removeLastOccurrence removeLastOccurrence}. jaroslav@597: * jaroslav@597: *

Unlike the {@link List} interface, this interface does not jaroslav@597: * provide support for indexed access to elements. jaroslav@597: * jaroslav@597: *

While Deque implementations are not strictly required jaroslav@597: * to prohibit the insertion of null elements, they are strongly jaroslav@597: * encouraged to do so. Users of any Deque implementations jaroslav@597: * that do allow null elements are strongly encouraged not to jaroslav@597: * take advantage of the ability to insert nulls. This is so because jaroslav@597: * null is used as a special return value by various methods jaroslav@597: * to indicated that the deque is empty. jaroslav@597: * jaroslav@597: *

Deque implementations generally do not define jaroslav@597: * element-based versions of the equals and hashCode jaroslav@597: * methods, but instead inherit the identity-based versions from class jaroslav@597: * Object. jaroslav@597: * jaroslav@597: *

This interface is a member of the Java Collections jaroslav@597: * Framework. jaroslav@597: * jaroslav@597: * @author Doug Lea jaroslav@597: * @author Josh Bloch jaroslav@597: * @since 1.6 jaroslav@597: * @param the type of elements held in this collection jaroslav@597: */ jaroslav@597: jaroslav@597: public interface Deque extends Queue { jaroslav@597: /** jaroslav@597: * Inserts the specified element at the front of this deque if it is jaroslav@597: * possible to do so immediately without violating capacity restrictions. jaroslav@597: * When using a capacity-restricted deque, it is generally preferable to jaroslav@597: * use method {@link #offerFirst}. jaroslav@597: * jaroslav@597: * @param e the element to add jaroslav@597: * @throws IllegalStateException if the element cannot be added at this jaroslav@597: * time due to capacity restrictions jaroslav@597: * @throws ClassCastException if the class of the specified element jaroslav@597: * prevents it from being added to this deque jaroslav@597: * @throws NullPointerException if the specified element is null and this jaroslav@597: * deque does not permit null elements jaroslav@597: * @throws IllegalArgumentException if some property of the specified jaroslav@597: * element prevents it from being added to this deque jaroslav@597: */ jaroslav@597: void addFirst(E e); jaroslav@597: jaroslav@597: /** jaroslav@597: * Inserts the specified element at the end of this deque if it is jaroslav@597: * possible to do so immediately without violating capacity restrictions. jaroslav@597: * When using a capacity-restricted deque, it is generally preferable to jaroslav@597: * use method {@link #offerLast}. jaroslav@597: * jaroslav@597: *

This method is equivalent to {@link #add}. jaroslav@597: * jaroslav@597: * @param e the element to add jaroslav@597: * @throws IllegalStateException if the element cannot be added at this jaroslav@597: * time due to capacity restrictions jaroslav@597: * @throws ClassCastException if the class of the specified element jaroslav@597: * prevents it from being added to this deque jaroslav@597: * @throws NullPointerException if the specified element is null and this jaroslav@597: * deque does not permit null elements jaroslav@597: * @throws IllegalArgumentException if some property of the specified jaroslav@597: * element prevents it from being added to this deque jaroslav@597: */ jaroslav@597: void addLast(E e); jaroslav@597: jaroslav@597: /** jaroslav@597: * Inserts the specified element at the front of this deque unless it would jaroslav@597: * violate capacity restrictions. When using a capacity-restricted deque, jaroslav@597: * this method is generally preferable to the {@link #addFirst} method, jaroslav@597: * which can fail to insert an element only by throwing an exception. jaroslav@597: * jaroslav@597: * @param e the element to add jaroslav@597: * @return true if the element was added to this deque, else jaroslav@597: * false jaroslav@597: * @throws ClassCastException if the class of the specified element jaroslav@597: * prevents it from being added to this deque jaroslav@597: * @throws NullPointerException if the specified element is null and this jaroslav@597: * deque does not permit null elements jaroslav@597: * @throws IllegalArgumentException if some property of the specified jaroslav@597: * element prevents it from being added to this deque jaroslav@597: */ jaroslav@597: boolean offerFirst(E e); jaroslav@597: jaroslav@597: /** jaroslav@597: * Inserts the specified element at the end of this deque unless it would jaroslav@597: * violate capacity restrictions. When using a capacity-restricted deque, jaroslav@597: * this method is generally preferable to the {@link #addLast} method, jaroslav@597: * which can fail to insert an element only by throwing an exception. jaroslav@597: * jaroslav@597: * @param e the element to add jaroslav@597: * @return true if the element was added to this deque, else jaroslav@597: * false jaroslav@597: * @throws ClassCastException if the class of the specified element jaroslav@597: * prevents it from being added to this deque jaroslav@597: * @throws NullPointerException if the specified element is null and this jaroslav@597: * deque does not permit null elements jaroslav@597: * @throws IllegalArgumentException if some property of the specified jaroslav@597: * element prevents it from being added to this deque jaroslav@597: */ jaroslav@597: boolean offerLast(E e); jaroslav@597: jaroslav@597: /** jaroslav@597: * Retrieves and removes the first element of this deque. This method jaroslav@597: * differs from {@link #pollFirst pollFirst} only in that it throws an jaroslav@597: * exception if this deque is empty. jaroslav@597: * jaroslav@597: * @return the head of this deque jaroslav@597: * @throws NoSuchElementException if this deque is empty jaroslav@597: */ jaroslav@597: E removeFirst(); jaroslav@597: jaroslav@597: /** jaroslav@597: * Retrieves and removes the last element of this deque. This method jaroslav@597: * differs from {@link #pollLast pollLast} only in that it throws an jaroslav@597: * exception if this deque is empty. jaroslav@597: * jaroslav@597: * @return the tail of this deque jaroslav@597: * @throws NoSuchElementException if this deque is empty jaroslav@597: */ jaroslav@597: E removeLast(); jaroslav@597: jaroslav@597: /** jaroslav@597: * Retrieves and removes the first element of this deque, jaroslav@597: * or returns null if this deque is empty. jaroslav@597: * jaroslav@597: * @return the head of this deque, or null if this deque is empty jaroslav@597: */ jaroslav@597: E pollFirst(); jaroslav@597: jaroslav@597: /** jaroslav@597: * Retrieves and removes the last element of this deque, jaroslav@597: * or returns null if this deque is empty. jaroslav@597: * jaroslav@597: * @return the tail of this deque, or null if this deque is empty jaroslav@597: */ jaroslav@597: E pollLast(); jaroslav@597: jaroslav@597: /** jaroslav@597: * Retrieves, but does not remove, the first element of this deque. jaroslav@597: * jaroslav@597: * This method differs from {@link #peekFirst peekFirst} only in that it jaroslav@597: * throws an exception if this deque is empty. jaroslav@597: * jaroslav@597: * @return the head of this deque jaroslav@597: * @throws NoSuchElementException if this deque is empty jaroslav@597: */ jaroslav@597: E getFirst(); jaroslav@597: jaroslav@597: /** jaroslav@597: * Retrieves, but does not remove, the last element of this deque. jaroslav@597: * This method differs from {@link #peekLast peekLast} only in that it jaroslav@597: * throws an exception if this deque is empty. jaroslav@597: * jaroslav@597: * @return the tail of this deque jaroslav@597: * @throws NoSuchElementException if this deque is empty jaroslav@597: */ jaroslav@597: E getLast(); jaroslav@597: jaroslav@597: /** jaroslav@597: * Retrieves, but does not remove, the first element of this deque, jaroslav@597: * or returns null if this deque is empty. jaroslav@597: * jaroslav@597: * @return the head of this deque, or null if this deque is empty jaroslav@597: */ jaroslav@597: E peekFirst(); jaroslav@597: jaroslav@597: /** jaroslav@597: * Retrieves, but does not remove, the last element of this deque, jaroslav@597: * or returns null if this deque is empty. jaroslav@597: * jaroslav@597: * @return the tail of this deque, or null if this deque is empty jaroslav@597: */ jaroslav@597: E peekLast(); jaroslav@597: jaroslav@597: /** jaroslav@597: * Removes the first occurrence of the specified element from this deque. jaroslav@597: * If the deque does not contain the element, it is unchanged. jaroslav@597: * More formally, removes the first element e such that jaroslav@597: * (o==null ? e==null : o.equals(e)) jaroslav@597: * (if such an element exists). jaroslav@597: * Returns true if this deque contained the specified element jaroslav@597: * (or equivalently, if this deque changed as a result of the call). jaroslav@597: * jaroslav@597: * @param o element to be removed from this deque, if present jaroslav@597: * @return true if an element was removed as a result of this call jaroslav@597: * @throws ClassCastException if the class of the specified element jaroslav@597: * is incompatible with this deque jaroslav@597: * (optional) jaroslav@597: * @throws NullPointerException if the specified element is null and this jaroslav@597: * deque does not permit null elements jaroslav@597: * (optional) jaroslav@597: */ jaroslav@597: boolean removeFirstOccurrence(Object o); jaroslav@597: jaroslav@597: /** jaroslav@597: * Removes the last occurrence of the specified element from this deque. jaroslav@597: * If the deque does not contain the element, it is unchanged. jaroslav@597: * More formally, removes the last element e such that jaroslav@597: * (o==null ? e==null : o.equals(e)) jaroslav@597: * (if such an element exists). jaroslav@597: * Returns true if this deque contained the specified element jaroslav@597: * (or equivalently, if this deque changed as a result of the call). jaroslav@597: * jaroslav@597: * @param o element to be removed from this deque, if present jaroslav@597: * @return true if an element was removed as a result of this call jaroslav@597: * @throws ClassCastException if the class of the specified element jaroslav@597: * is incompatible with this deque jaroslav@597: * (optional) jaroslav@597: * @throws NullPointerException if the specified element is null and this jaroslav@597: * deque does not permit null elements jaroslav@597: * (optional) jaroslav@597: */ jaroslav@597: boolean removeLastOccurrence(Object o); jaroslav@597: jaroslav@597: // *** Queue methods *** jaroslav@597: jaroslav@597: /** jaroslav@597: * Inserts the specified element into the queue represented by this deque jaroslav@597: * (in other words, at the tail of this deque) if it is possible to do so jaroslav@597: * immediately without violating capacity restrictions, returning jaroslav@597: * true upon success and throwing an jaroslav@597: * IllegalStateException if no space is currently available. jaroslav@597: * When using a capacity-restricted deque, it is generally preferable to jaroslav@597: * use {@link #offer(Object) offer}. jaroslav@597: * jaroslav@597: *

This method is equivalent to {@link #addLast}. jaroslav@597: * jaroslav@597: * @param e the element to add jaroslav@597: * @return true (as specified by {@link Collection#add}) jaroslav@597: * @throws IllegalStateException if the element cannot be added at this jaroslav@597: * time due to capacity restrictions jaroslav@597: * @throws ClassCastException if the class of the specified element jaroslav@597: * prevents it from being added to this deque jaroslav@597: * @throws NullPointerException if the specified element is null and this jaroslav@597: * deque does not permit null elements jaroslav@597: * @throws IllegalArgumentException if some property of the specified jaroslav@597: * element prevents it from being added to this deque jaroslav@597: */ jaroslav@597: boolean add(E e); jaroslav@597: jaroslav@597: /** jaroslav@597: * Inserts the specified element into the queue represented by this deque jaroslav@597: * (in other words, at the tail of this deque) if it is possible to do so jaroslav@597: * immediately without violating capacity restrictions, returning jaroslav@597: * true upon success and false if no space is currently jaroslav@597: * available. When using a capacity-restricted deque, this method is jaroslav@597: * generally preferable to the {@link #add} method, which can fail to jaroslav@597: * insert an element only by throwing an exception. jaroslav@597: * jaroslav@597: *

This method is equivalent to {@link #offerLast}. jaroslav@597: * jaroslav@597: * @param e the element to add jaroslav@597: * @return true if the element was added to this deque, else jaroslav@597: * false jaroslav@597: * @throws ClassCastException if the class of the specified element jaroslav@597: * prevents it from being added to this deque jaroslav@597: * @throws NullPointerException if the specified element is null and this jaroslav@597: * deque does not permit null elements jaroslav@597: * @throws IllegalArgumentException if some property of the specified jaroslav@597: * element prevents it from being added to this deque jaroslav@597: */ jaroslav@597: boolean offer(E e); jaroslav@597: jaroslav@597: /** jaroslav@597: * Retrieves and removes the head of the queue represented by this deque jaroslav@597: * (in other words, the first element of this deque). jaroslav@597: * This method differs from {@link #poll poll} only in that it throws an jaroslav@597: * exception if this deque is empty. jaroslav@597: * jaroslav@597: *

This method is equivalent to {@link #removeFirst()}. jaroslav@597: * jaroslav@597: * @return the head of the queue represented by this deque jaroslav@597: * @throws NoSuchElementException if this deque is empty jaroslav@597: */ jaroslav@597: E remove(); jaroslav@597: jaroslav@597: /** jaroslav@597: * Retrieves and removes the head of the queue represented by this deque jaroslav@597: * (in other words, the first element of this deque), or returns jaroslav@597: * null if this deque is empty. jaroslav@597: * jaroslav@597: *

This method is equivalent to {@link #pollFirst()}. jaroslav@597: * jaroslav@597: * @return the first element of this deque, or null if jaroslav@597: * this deque is empty jaroslav@597: */ jaroslav@597: E poll(); jaroslav@597: jaroslav@597: /** jaroslav@597: * Retrieves, but does not remove, the head of the queue represented by jaroslav@597: * this deque (in other words, the first element of this deque). jaroslav@597: * This method differs from {@link #peek peek} only in that it throws an jaroslav@597: * exception if this deque is empty. jaroslav@597: * jaroslav@597: *

This method is equivalent to {@link #getFirst()}. jaroslav@597: * jaroslav@597: * @return the head of the queue represented by this deque jaroslav@597: * @throws NoSuchElementException if this deque is empty jaroslav@597: */ jaroslav@597: E element(); jaroslav@597: jaroslav@597: /** jaroslav@597: * Retrieves, but does not remove, the head of the queue represented by jaroslav@597: * this deque (in other words, the first element of this deque), or jaroslav@597: * returns null if this deque is empty. jaroslav@597: * jaroslav@597: *

This method is equivalent to {@link #peekFirst()}. jaroslav@597: * jaroslav@597: * @return the head of the queue represented by this deque, or jaroslav@597: * null if this deque is empty jaroslav@597: */ jaroslav@597: E peek(); jaroslav@597: jaroslav@597: jaroslav@597: // *** Stack methods *** jaroslav@597: jaroslav@597: /** jaroslav@597: * Pushes an element onto the stack represented by this deque (in other jaroslav@597: * words, at the head of this deque) if it is possible to do so jaroslav@597: * immediately without violating capacity restrictions, returning jaroslav@597: * true upon success and throwing an jaroslav@597: * IllegalStateException if no space is currently available. jaroslav@597: * jaroslav@597: *

This method is equivalent to {@link #addFirst}. jaroslav@597: * jaroslav@597: * @param e the element to push jaroslav@597: * @throws IllegalStateException if the element cannot be added at this jaroslav@597: * time due to capacity restrictions jaroslav@597: * @throws ClassCastException if the class of the specified element jaroslav@597: * prevents it from being added to this deque jaroslav@597: * @throws NullPointerException if the specified element is null and this jaroslav@597: * deque does not permit null elements jaroslav@597: * @throws IllegalArgumentException if some property of the specified jaroslav@597: * element prevents it from being added to this deque jaroslav@597: */ jaroslav@597: void push(E e); jaroslav@597: jaroslav@597: /** jaroslav@597: * Pops an element from the stack represented by this deque. In other jaroslav@597: * words, removes and returns the first element of this deque. jaroslav@597: * jaroslav@597: *

This method is equivalent to {@link #removeFirst()}. jaroslav@597: * jaroslav@597: * @return the element at the front of this deque (which is the top jaroslav@597: * of the stack represented by this deque) jaroslav@597: * @throws NoSuchElementException if this deque is empty jaroslav@597: */ jaroslav@597: E pop(); jaroslav@597: jaroslav@597: jaroslav@597: // *** Collection methods *** jaroslav@597: jaroslav@597: /** jaroslav@597: * Removes the first occurrence of the specified element from this deque. jaroslav@597: * If the deque does not contain the element, it is unchanged. jaroslav@597: * More formally, removes the first element e such that jaroslav@597: * (o==null ? e==null : o.equals(e)) jaroslav@597: * (if such an element exists). jaroslav@597: * Returns true if this deque contained the specified element jaroslav@597: * (or equivalently, if this deque changed as a result of the call). jaroslav@597: * jaroslav@597: *

This method is equivalent to {@link #removeFirstOccurrence}. jaroslav@597: * jaroslav@597: * @param o element to be removed from this deque, if present jaroslav@597: * @return true if an element was removed as a result of this call jaroslav@597: * @throws ClassCastException if the class of the specified element jaroslav@597: * is incompatible with this deque jaroslav@597: * (optional) jaroslav@597: * @throws NullPointerException if the specified element is null and this jaroslav@597: * deque does not permit null elements jaroslav@597: * (optional) jaroslav@597: */ jaroslav@597: boolean remove(Object o); jaroslav@597: jaroslav@597: /** jaroslav@597: * Returns true if this deque contains the specified element. jaroslav@597: * More formally, returns true if and only if this deque contains jaroslav@597: * at least one element e such that jaroslav@597: * (o==null ? e==null : o.equals(e)). jaroslav@597: * jaroslav@597: * @param o element whose presence in this deque is to be tested jaroslav@597: * @return true if this deque contains the specified element jaroslav@597: * @throws ClassCastException if the type of the specified element jaroslav@597: * is incompatible with this deque jaroslav@597: * (optional) jaroslav@597: * @throws NullPointerException if the specified element is null and this jaroslav@597: * deque does not permit null elements jaroslav@597: * (optional) jaroslav@597: */ jaroslav@597: boolean contains(Object o); jaroslav@597: jaroslav@597: /** jaroslav@597: * Returns the number of elements in this deque. jaroslav@597: * jaroslav@597: * @return the number of elements in this deque jaroslav@597: */ jaroslav@597: public int size(); jaroslav@597: jaroslav@597: /** jaroslav@597: * Returns an iterator over the elements in this deque in proper sequence. jaroslav@597: * The elements will be returned in order from first (head) to last (tail). jaroslav@597: * jaroslav@597: * @return an iterator over the elements in this deque in proper sequence jaroslav@597: */ jaroslav@597: Iterator iterator(); jaroslav@597: jaroslav@597: /** jaroslav@597: * Returns an iterator over the elements in this deque in reverse jaroslav@597: * sequential order. The elements will be returned in order from jaroslav@597: * last (tail) to first (head). jaroslav@597: * jaroslav@597: * @return an iterator over the elements in this deque in reverse jaroslav@597: * sequence jaroslav@597: */ jaroslav@597: Iterator descendingIterator(); jaroslav@597: jaroslav@597: }