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 (21 years 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
#	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			* does <em>not</em> allow null elements.
15			*/
16	dl	1.2
17	tim	1.1	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			}