java/util/AbstractQueue.java

/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain. Use, modify, and
 * redistribute this code in any way without acknowledgement.
 */

package java.util;

/**
 * AbstractQueue provides default implementations of add, remove, and
 * element based on offer, poll, and peek, respectively but that throw
 * exceptions instead of indicating failure via false or null returns.
 * The provided implementations all assume that the base implementation
 * does <em>not</em> allow <tt>null</tt> elements.
 * @since 1.5
 * @author Doug Lea
 */

public abstract class AbstractQueue<E> extends AbstractCollection<E> implements Queue<E> {

    public boolean add(E x) {
        if (offer(x))
            return true;
        else
            throw new IllegalStateException("Queue full");
    }

    public E remove() {
        E x = poll();
        if (x != null)
            return x;
        else
            throw new NoSuchElementException();
    }

    public E element() {
        E x = peek();
        if (x != null)
            return x;
        else
            throw new NoSuchElementException();
    }

    public void clear() {
        while (poll() != null)
            ;
    }

    public abstract Iterator<E> iterator();
}
Revision:	1.5
Committed:	Sat Jul 26 13:17:51 2003 UTC (20 years, 10 months ago) by tim
Branch:	MAIN
Changes since 1.4:	+2 -1 lines
Log Message:	Default compiler is now 2.2-ea. Some sources are not compatible with 2.0-ea.
#	User	Rev	Content
1	dl	1.2	/*
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	tim	1.1	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	brian	1.3	* does <em>not</em> allow <tt>null</tt> elements.
15	dl	1.4	* @since 1.5
16			* @author Doug Lea
17	tim	1.1	*/
18	tim	1.5
19	tim	1.1	public abstract class AbstractQueue<E> extends AbstractCollection<E> implements Queue<E> {
20
21			public boolean add(E x) {
22			if (offer(x))
23			return true;
24			else
25			throw new IllegalStateException("Queue full");
26			}
27
28			public E remove() {
29			E x = poll();
30			if (x != null)
31			return x;
32			else
33			throw new NoSuchElementException();
34			}
35
36			public E element() {
37			E x = peek();
38			if (x != null)
39			return x;
40			else
41			throw new NoSuchElementException();
42			}
43
44			public void clear() {
45			while (poll() != null)
46			;
47			}
48
49	tim	1.5	public abstract Iterator<E> iterator();
50	tim	1.1	}