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 null elements.
 */
 
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)
            ;
    }

}
Revision:	1.2
Committed:	Tue May 27 18:20:06 2003 UTC (20 years, 11 months ago) by dl
Branch:	MAIN
CVS Tags:	JSR166_PRELIMINARY_TEST_RELEASE_1, JSR166_PRERELEASE_0_1
Changes since 1.1:	+7 -0 lines
Log Message:	re-checkin initial implementations
#	Content
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.
15	*/
16
17	public abstract class AbstractQueue<E> extends AbstractCollection<E> implements Queue<E> {
18
19	public boolean add(E x) {
20	if (offer(x))
21	return true;
22	else
23	throw new IllegalStateException("Queue full");
24	}
25
26	public E remove() {
27	E x = poll();
28	if (x != null)
29	return x;
30	else
31	throw new NoSuchElementException();
32	}
33
34	public E element() {
35	E x = peek();
36	if (x != null)
37	return x;
38	else
39	throw new NoSuchElementException();
40	}
41
42	public void clear() {
43	while (poll() != null)
44	;
45	}
46
47	}