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 with assistance from members of JCP JSR-166
jaroslav@597:  * Expert Group and released to the public domain, as explained at
jaroslav@597:  * http://creativecommons.org/publicdomain/zero/1.0/
jaroslav@597:  */
jaroslav@597: 
jaroslav@597: package java.util;
jaroslav@597: 
jaroslav@597: /**
jaroslav@597:  * This class provides skeletal implementations of some {@link Queue}
jaroslav@597:  * operations. The implementations in this class are appropriate when
jaroslav@597:  * the base implementation does <em>not</em> allow <tt>null</tt>
jaroslav@597:  * elements.  Methods {@link #add add}, {@link #remove remove}, and
jaroslav@597:  * {@link #element element} are based on {@link #offer offer}, {@link
jaroslav@597:  * #poll poll}, and {@link #peek peek}, respectively, but throw
jaroslav@597:  * exceptions instead of indicating failure via <tt>false</tt> or
jaroslav@597:  * <tt>null</tt> returns.
jaroslav@597:  *
jaroslav@597:  * <p>A <tt>Queue</tt> implementation that extends this class must
jaroslav@597:  * minimally define a method {@link Queue#offer} which does not permit
jaroslav@597:  * insertion of <tt>null</tt> elements, along with methods {@link
jaroslav@597:  * Queue#peek}, {@link Queue#poll}, {@link Collection#size}, and
jaroslav@597:  * {@link Collection#iterator}.  Typically, additional methods will be
jaroslav@597:  * overridden as well.  If these requirements cannot be met, consider
jaroslav@597:  * instead subclassing {@link AbstractCollection}.
jaroslav@597:  *
jaroslav@597:  * <p>This class is a member of the
jaroslav@597:  * <a href="{@docRoot}/../technotes/guides/collections/index.html">
jaroslav@597:  * Java Collections Framework</a>.
jaroslav@597:  *
jaroslav@597:  * @since 1.5
jaroslav@597:  * @author Doug Lea
jaroslav@597:  * @param <E> the type of elements held in this collection
jaroslav@597:  */
jaroslav@597: public abstract class AbstractQueue<E>
jaroslav@597:     extends AbstractCollection<E>
jaroslav@597:     implements Queue<E> {
jaroslav@597: 
jaroslav@597:     /**
jaroslav@597:      * Constructor for use by subclasses.
jaroslav@597:      */
jaroslav@597:     protected AbstractQueue() {
jaroslav@597:     }
jaroslav@597: 
jaroslav@597:     /**
jaroslav@597:      * Inserts the specified element into this queue if it is possible to do so
jaroslav@597:      * immediately without violating capacity restrictions, returning
jaroslav@597:      * <tt>true</tt> upon success and throwing an <tt>IllegalStateException</tt>
jaroslav@597:      * if no space is currently available.
jaroslav@597:      *
jaroslav@597:      * <p>This implementation returns <tt>true</tt> if <tt>offer</tt> succeeds,
jaroslav@597:      * else throws an <tt>IllegalStateException</tt>.
jaroslav@597:      *
jaroslav@597:      * @param e the element to add
jaroslav@597:      * @return <tt>true</tt> (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 queue
jaroslav@597:      * @throws NullPointerException if the specified element is null and
jaroslav@597:      *         this queue does not permit null elements
jaroslav@597:      * @throws IllegalArgumentException if some property of this element
jaroslav@597:      *         prevents it from being added to this queue
jaroslav@597:      */
jaroslav@597:     public boolean add(E e) {
jaroslav@597:         if (offer(e))
jaroslav@597:             return true;
jaroslav@597:         else
jaroslav@597:             throw new IllegalStateException("Queue full");
jaroslav@597:     }
jaroslav@597: 
jaroslav@597:     /**
jaroslav@597:      * Retrieves and removes the head of this queue.  This method differs
jaroslav@597:      * from {@link #poll poll} only in that it throws an exception if this
jaroslav@597:      * queue is empty.
jaroslav@597:      *
jaroslav@597:      * <p>This implementation returns the result of <tt>poll</tt>
jaroslav@597:      * unless the queue is empty.
jaroslav@597:      *
jaroslav@597:      * @return the head of this queue
jaroslav@597:      * @throws NoSuchElementException if this queue is empty
jaroslav@597:      */
jaroslav@597:     public E remove() {
jaroslav@597:         E x = poll();
jaroslav@597:         if (x != null)
jaroslav@597:             return x;
jaroslav@597:         else
jaroslav@597:             throw new NoSuchElementException();
jaroslav@597:     }
jaroslav@597: 
jaroslav@597:     /**
jaroslav@597:      * Retrieves, but does not remove, the head of this queue.  This method
jaroslav@597:      * differs from {@link #peek peek} only in that it throws an exception if
jaroslav@597:      * this queue is empty.
jaroslav@597:      *
jaroslav@597:      * <p>This implementation returns the result of <tt>peek</tt>
jaroslav@597:      * unless the queue is empty.
jaroslav@597:      *
jaroslav@597:      * @return the head of this queue
jaroslav@597:      * @throws NoSuchElementException if this queue is empty
jaroslav@597:      */
jaroslav@597:     public E element() {
jaroslav@597:         E x = peek();
jaroslav@597:         if (x != null)
jaroslav@597:             return x;
jaroslav@597:         else
jaroslav@597:             throw new NoSuchElementException();
jaroslav@597:     }
jaroslav@597: 
jaroslav@597:     /**
jaroslav@597:      * Removes all of the elements from this queue.
jaroslav@597:      * The queue will be empty after this call returns.
jaroslav@597:      *
jaroslav@597:      * <p>This implementation repeatedly invokes {@link #poll poll} until it
jaroslav@597:      * returns <tt>null</tt>.
jaroslav@597:      */
jaroslav@597:     public void clear() {
jaroslav@597:         while (poll() != null)
jaroslav@597:             ;
jaroslav@597:     }
jaroslav@597: 
jaroslav@597:     /**
jaroslav@597:      * Adds all of the elements in the specified collection to this
jaroslav@597:      * queue.  Attempts to addAll of a queue to itself result in
jaroslav@597:      * <tt>IllegalArgumentException</tt>. Further, the behavior of
jaroslav@597:      * this operation is undefined if the specified collection is
jaroslav@597:      * modified while the operation is in progress.
jaroslav@597:      *
jaroslav@597:      * <p>This implementation iterates over the specified collection,
jaroslav@597:      * and adds each element returned by the iterator to this
jaroslav@597:      * queue, in turn.  A runtime exception encountered while
jaroslav@597:      * trying to add an element (including, in particular, a
jaroslav@597:      * <tt>null</tt> element) may result in only some of the elements
jaroslav@597:      * having been successfully added when the associated exception is
jaroslav@597:      * thrown.
jaroslav@597:      *
jaroslav@597:      * @param c collection containing elements to be added to this queue
jaroslav@597:      * @return <tt>true</tt> if this queue changed as a result of the call
jaroslav@597:      * @throws ClassCastException if the class of an element of the specified
jaroslav@597:      *         collection prevents it from being added to this queue
jaroslav@597:      * @throws NullPointerException if the specified collection contains a
jaroslav@597:      *         null element and this queue does not permit null elements,
jaroslav@597:      *         or if the specified collection is null
jaroslav@597:      * @throws IllegalArgumentException if some property of an element of the
jaroslav@597:      *         specified collection prevents it from being added to this
jaroslav@597:      *         queue, or if the specified collection is this queue
jaroslav@597:      * @throws IllegalStateException if not all the elements can be added at
jaroslav@597:      *         this time due to insertion restrictions
jaroslav@597:      * @see #add(Object)
jaroslav@597:      */
jaroslav@597:     public boolean addAll(Collection<? extends E> c) {
jaroslav@597:         if (c == null)
jaroslav@597:             throw new NullPointerException();
jaroslav@597:         if (c == this)
jaroslav@597:             throw new IllegalArgumentException();
jaroslav@597:         boolean modified = false;
jaroslav@597:         for (E e : c)
jaroslav@597:             if (add(e))
jaroslav@597:                 modified = true;
jaroslav@597:         return modified;
jaroslav@597:     }
jaroslav@597: 
jaroslav@597: }