/*
* 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 com.smartandroid.sa.zUImageLoader.core.assist.deque;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.Queue;
import java.util.Stack;
/**
* 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 summarized in the following 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>Special value</em></td>
* <td ALIGN=CENTER><em>Throws exception</em></td>
* <td ALIGN=CENTER><em>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 at 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>
* <td>{@link java.util.Queue#add add(e)}</td>
* <td>{@link #addLast addLast(e)}</td>
* </tr>
* <tr>
* <td>{@link java.util.Queue#offer offer(e)}</td>
* <td>{@link #offerLast offerLast(e)}</td>
* </tr>
* <tr>
* <td>{@link java.util.Queue#remove remove()}</td>
* <td>{@link #removeFirst removeFirst()}</td>
* </tr>
* <tr>
* <td>{@link java.util.Queue#poll poll()}</td>
* <td>{@link #pollFirst pollFirst()}</td>
* </tr>
* <tr>
* <td>{@link java.util.Queue#element element()}</td>
* <td>{@link #getFirst getFirst()}</td>
* </tr>
* <tr>
* <td>{@link java.util.Queue#peek peek()}</td>
* <td>{@link #peek peekFirst()}</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 deque
* 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>
* <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}.
*
* <p>
* 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>.
*
* @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 at the front of this deque if it is
* possible to do so immediately without violating capacity restrictions.
* When using a capacity-restricted deque, it is generally preferable to use
* method {@link #offerFirst}.
*
* @param e
* the element to add
* @throws IllegalStateException
* if the element cannot be added at this time due to capacity
* restrictions
* @throws ClassCastException
* if the class of the specified element prevents it from being
* added to this deque
* @throws NullPointerException
* if the specified element is null and this deque does not
* permit null elements
* @throws IllegalArgumentException
* if some property of the specified element prevents it from
* being added to this deque
*/
void addFirst(E e);
/**
* Inserts the specified element at the end of this deque if it is possible
* to do so immediately without violating capacity restrictions. When using
* a capacity-restricted deque, it is generally preferable to use method
* {@link #offerLast}.
*
* <p>
* This method is equivalent to {@link #add}.
*
* @param e
* the element to add
* @throws IllegalStateException
* if the element cannot be added at this time due to capacity
* restrictions
* @throws ClassCastException
* if the class of the specified element prevents it from being
* added to this deque
* @throws NullPointerException
* if the specified element is null and this deque does not
* permit null elements
* @throws IllegalArgumentException
* if some property of the specified element prevents it from
* being added to this deque
*/
void addLast(E e);
/**
* Inserts the specified element at the front of this deque unless it would
* violate capacity restrictions. When using a capacity-restricted deque,
* this method is generally preferable to the {@link #addFirst} method,
* which can fail to insert an element only by throwing an exception.
*
* @param e
* the element to add
* @return <tt>true</tt> if the element was added to this deque, else
* <tt>false</tt>
* @throws ClassCastException
* if the class of the specified element prevents it from being
* added to this deque
* @throws NullPointerException
* if the specified element is null and this deque does not
* permit null elements
* @throws IllegalArgumentException
* if some property of the specified element prevents it from
* being added to this deque
*/
boolean offerFirst(E e);
/**
* Inserts the specified element at the end of this deque unless it would
* violate capacity restrictions. When using a capacity-restricted deque,
* this method is generally preferable to the {@link #addLast} method, which
* can fail to insert an element only by throwing an exception.
*
* @param e
* the element to add
* @return <tt>true</tt> if the element was added to this deque, else
* <tt>false</tt>
* @throws ClassCastException
* if the class of the specified element prevents it from being
* added to this deque
* @throws NullPointerException
* if the specified element is null and this deque does not
* permit null elements
* @throws IllegalArgumentException
* if some property of the specified element prevents it from
* being added to this deque
*/
boolean offerLast(E e);
/**
* Retrieves and removes the first element of this deque. This method
* differs from {@link #pollFirst pollFirst} only in that it throws an
* exception if this deque is empty.
*
* @return the head 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 {@link #pollLast pollLast} only in that it throws an exception if
* this deque is empty.
*
* @return the tail of this deque
* @throws NoSuchElementException
* if this deque is empty
*/
E removeLast();
/**
* Retrieves and removes the first element of this deque, or returns
* <tt>null</tt> if this deque is empty.
*
* @return the head of this deque, or <tt>null</tt> if this deque is empty
*/
E pollFirst();
/**
* Retrieves and removes the last element of this deque, or returns
* <tt>null</tt> if this deque is empty.
*
* @return the tail of this deque, or <tt>null</tt> if this deque is empty
*/
E pollLast();
/**
* Retrieves, but does not remove, the first element of this deque.
*
* This method differs from {@link #peekFirst peekFirst} only in that it
* throws an exception if this deque is empty.
*
* @return the head 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 {@link #peekLast peekLast} only in that it throws an
* exception if this deque is empty.
*
* @return the tail of this deque
* @throws NoSuchElementException
* if this deque is empty
*/
E getLast();
/**
* Retrieves, but does not remove, the first element of this deque, or
* returns <tt>null</tt> if this deque is empty.
*
* @return the head 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, or
* returns <tt>null</tt> if this deque is empty.
*
* @return the tail of this deque, or <tt>null</tt> if this deque is empty
*/
E peekLast();
/**
* 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 <tt>e</tt> such that
* <tt>(o==null ? e==null : o.equals(e))</tt> (if such
* an element exists). Returns <tt>true</tt> if this deque contained the
* specified element (or equivalently, if this deque changed as a result of
* the call).
*
* @param o
* element to be removed from this deque, if present
* @return <tt>true</tt> if an element was removed as a result of this call
* @throws ClassCastException
* if the class of the specified element is incompatible with
* this deque (optional)
* @throws NullPointerException
* if the specified element is null and this deque does not
* permit null elements (optional)
*/
boolean removeFirstOccurrence(Object o);
/**
* 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 <tt>e</tt> such that
* <tt>(o==null ? e==null : o.equals(e))</tt> (if such
* an element exists). Returns <tt>true</tt> if this deque contained the
* specified element (or equivalently, if this deque changed as a result of
* the call).
*
* @param o
* element to be removed from this deque, if present
* @return <tt>true</tt> if an element was removed as a result of this call
* @throws ClassCastException
* if the class of the specified element is incompatible with
* this deque (optional)
* @throws NullPointerException
* if the specified element is null and this deque does not
* permit null elements (optional)
*/
boolean removeLastOccurrence(Object o);
// *** Queue methods ***
/**
* 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
* <tt>true</tt> upon success and throwing an <tt>IllegalStateException</tt>
* if no space is currently available. When using a capacity-restricted
* deque, it is generally preferable to use {@link #offer offer}.
*
* <p>
* This method is equivalent to {@link #addLast}.
*
* @param e
* the element to add
* @return <tt>true</tt> (as specified by {@link Collection#add})
* @throws IllegalStateException
* if the element cannot be added at this time due to capacity
* restrictions
* @throws ClassCastException
* if the class of the specified element prevents it from being
* added to this deque
* @throws NullPointerException
* if the specified element is null and this deque does not
* permit null elements
* @throws IllegalArgumentException
* if some property of the specified element prevents it from
* being added to this deque
*/
boolean add(E e);
/**
* 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
* <tt>true</tt> upon success and <tt>false</tt> if no space is currently
* available. 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 add
* @return <tt>true</tt> if the element was added to this deque, else
* <tt>false</tt>
* @throws ClassCastException
* if the class of the specified element prevents it from being
* added to this deque
* @throws NullPointerException
* if the specified element is null and this deque does not
* permit null elements
* @throws IllegalArgumentException
* if some property of the specified element prevents it from
* being added to this deque
*/
boolean offer(E e);
/**
* Retrieves and removes the head of the queue represented by this deque (in
* other words, the first element of this deque). This method differs from
* {@link #poll poll} 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 and removes the head of the queue represented by this deque (in
* other words, the first element of this deque), or returns <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, but does not remove, the head of the queue represented by this
* deque (in other words, the first element of this deque). This method
* differs from {@link #peek peek} 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();
/**
* 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
* <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();
// *** Stack methods ***
/**
* 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, returning <tt>true</tt> upon
* success and throwing an <tt>IllegalStateException</tt> if no space is
* currently available.
*
* <p>
* This method is equivalent to {@link #addFirst}.
*
* @param e
* the element to push
* @throws IllegalStateException
* if the element cannot be added at this time due to capacity
* restrictions
* @throws ClassCastException
* if the class of the specified element prevents it from being
* added to this deque
* @throws NullPointerException
* if the specified element is null and this deque does not
* permit null elements
* @throws IllegalArgumentException
* if some property of the specified element prevents it from
* being added to this deque
*/
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 methods ***
/**
* 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 <tt>e</tt> such that
* <tt>(o==null ? e==null : o.equals(e))</tt> (if such
* an element exists). Returns <tt>true</tt> if this deque contained the
* specified element (or equivalently, if this deque changed as a result of
* the call).
*
* <p>
* This method is equivalent to {@link #removeFirstOccurrence}.
*
* @param o
* element to be removed from this deque, if present
* @return <tt>true</tt> if an element was removed as a result of this call
* @throws ClassCastException
* if the class of the specified element is incompatible with
* this deque (optional)
* @throws NullPointerException
* if the specified element is null and this deque does not
* permit null elements (optional)
*/
boolean remove(Object o);
/**
* Returns <tt>true</tt> if this deque contains the specified element. More
* formally, returns <tt>true</tt> if and only if this deque contains at
* least one element <tt>e</tt> such that
* <tt>(o==null ? e==null : o.equals(e))</tt>.
*
* @param o
* element whose presence in this deque is to be tested
* @return <tt>true</tt> if this deque contains the specified element
* @throws ClassCastException
* if the type of the specified element is incompatible with
* this deque (optional)
* @throws NullPointerException
* if the specified element is null and this deque does not
* permit null elements (optional)
*/
boolean contains(Object o);
/**
* Returns the number of elements in this deque.
*
* @return the number of elements in this deque
*/
public int size();
/**
* 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).
*
* @return an iterator over the elements in this deque in proper sequence
*/
Iterator<E> iterator();
/**
* 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).
*
* @return an iterator over the elements in this deque in reverse sequence
*/
Iterator<E> descendingIterator();
}