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root/jsr166/jsr166/src/main/java/util/AbstractQueue.java

Comparing jsr166/src/main/java/util/AbstractQueue.java (file contents):
Revision 1.1 by tim, Sun May 18 18:10:02 2003 UTC vs.
Revision 1.19 by dl, Sun Oct 5 22:59:21 2003 UTC

#	Line 1 | Line 1
1	+	/*
2	+	* Written by Doug Lea with assistance from members of JCP JSR-166
3	+	* Expert Group and released to the public domain. Use, modify, and
4	+	* redistribute this code in any way without acknowledgement.
5	+	*/
6	+
7		package java.util;
8
9		/**
10	<	* AbstractQueue provides default implementations of add, remove, and
11	<	* element based on offer, poll, and peek, respectively but that throw
12	<	* exceptions instead of indicating failure via false or null returns.
13	<	* The provided implementations all assume that the base implementation
14	<	* does <em>not</em> allow null elements.
10	>	* This class provides skeletal implementations of some {@link Queue}
11	>	* operations. The implementations in this class are appropriate when
12	>	* the base implementation does <em>not</em> allow <tt>null</tt>
13	>	* elements.  Methods {@link #add add}, {@link #remove remove}, and
14	>	* {@link #element element} are based on {@link #offer offer}, {@link
15	>	* #poll poll}, and {@link #peek peek}, respectively but throw
16	>	* exceptions instead of indicating failure via <tt>false</tt> or
17	>	* <tt>null</tt> returns.
18	>	*
19	>	* <p> A <tt>Queue</tt> implementation that extends this class must
20	>	* minimally define a method {@link Queue#offer} which does not permit
21	>	* insertion of <tt>null</tt> elements, along with methods {@link
22	>	* Queue#peek}, {@link Queue#poll}, {@link Collection#size}, and a
23	>	* {@link Collection#iterator} supporting {@link
24	>	* Iterator#remove}. Typically, additional methods will be overridden
25	>	* as well. If these requirements cannot be met, consider instead
26	>	* subclassing {@link AbstractCollection}.
27	>	*
28	>	* @since 1.5
29	>	* @author Doug Lea
30		*/
31	<	public abstract class AbstractQueue<E> extends AbstractCollection<E> implements Queue<E> {
31	>	public abstract class AbstractQueue<E>
32	>	extends AbstractCollection<E>
33	>	implements Queue<E> {
34	>
35	>	/**
36	>	* Constructor for use by subclasses.
37	>	*/
38	>	protected AbstractQueue() {
39	>	}
40	>
41
42	<	public boolean add(E x) {
43	<	if (offer(x))
42	>	/**
43	>	* Adds the specified element to this queue. This implementation
44	>	* returns <tt>true</tt> if <tt>offer</tt> succeeds, else
45	>	* throws an IllegalStateException.
46	>	*
47	>	* @param o the element
48	>	* @return <tt>true</tt> (as per the general contract of
49	>	*         <tt>Collection.add</tt>).
50	>	*
51	>	* @throws NullPointerException if the specified element is <tt>null</tt>
52	>	* @throws IllegalStateException if element cannot be added
53	>	*/
54	>	public boolean add(E o) {
55	>	if (offer(o))
56		return true;
57		else
58		throw new IllegalStateException("Queue full");
59		}
60
61	+	/**
62	+	* Retrieves and removes the head of this queue.
63	+	* This implementation returns the result of <tt>poll</tt>
64	+	* unless the queue is empty.
65	+	*
66	+	* @return the head of this queue.
67	+	* @throws NoSuchElementException if this queue is empty.
68	+	*/
69		public E remove() {
70		E x = poll();
71		if (x != null)
#	Line 24 | Line 74 | public abstract class AbstractQueue<E> e
74		throw new NoSuchElementException();
75		}
76
77	+
78	+	/**
79	+	* Retrieves, but does not remove, the head of this queue.
80	+	* This implementation returns the result of <tt>peek</tt>
81	+	* unless the queue is empty.
82	+	*
83	+	* @return the head of this queue.
84	+	* @throws NoSuchElementException if this queue is empty.
85	+	*/
86		public E element() {
87		E x = peek();
88		if (x != null)
#	Line 32 | Line 91 | public abstract class AbstractQueue<E> e
91		throw new NoSuchElementException();
92		}
93
94	+	/**
95	+	* Removes all of the elements from this collection.
96	+	* The collection will be empty after this call returns.
97	+	* <p>This implementation repeatedly invokes {@link #poll poll} until it
98	+	* returns <tt>null</tt>.
99	+	*/
100		public void clear() {
101		while (poll() != null)
102		;
103		}
104
105	+	/**
106	+	* Adds all of the elements in the specified collection to this
107	+	* queue.  Attempts to addAll of a queue to itself result in
108	+	* <tt>IllegalArgumentException</tt>. Further, the behavior of
109	+	* this operation is undefined if the specified collection is
110	+	* modified while the operation is in progress.
111	+	*
112	+	* <p>This implementation iterates over the specified collection,
113	+	* and adds each element returned by the iterator to this
114	+	* collection, in turn.  A runtime exception encountered while
115	+	* trying to add an element (including, in particular, a
116	+	* <tt>null</tt> element) may result in only some of the elements
117	+	* having been successfully added when the associated exception is
118	+	* thrown.
119	+	*
120	+	* @param c collection whose elements are to be added to this collection.
121	+	* @return <tt>true</tt> if this collection changed as a result of the
122	+	*         call.
123	+	* @throws NullPointerException if the specified collection, or
124	+	* any of its elements are null.
125	+	* @throws IllegalArgumentException if c is this queue.
126	+	*
127	+	* @see #add(Object)
128	+	*/
129	+	public boolean addAll(Collection<? extends E> c) {
130	+	if (c == null)
131	+	throw new NullPointerException();
132	+	if (c == this)
133	+	throw new IllegalArgumentException();
134	+	boolean modified = false;
135	+	Iterator<? extends E> e = c.iterator();
136	+	while (e.hasNext()) {
137	+	if (add(e.next()))
138	+	modified = true;
139	+	}
140	+	return modified;
141	+	}
142	+
143		}

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