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.
#	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 <tt>null</tt> elements.
15	* @since 1.5
16	* @author Doug Lea
17	*/
18
19	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	public abstract Iterator<E> iterator();
50	}