java/util/AbstractQueue.java

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:	1.1
Committed:	Sun May 18 18:10:02 2003 UTC (21 years ago) by tim
Branch:	MAIN
Log Message:	Copied Queue, AbstractQueue, and PriorityQueue from src/dl, fixed some type parameterization, and added some basic tests. Added control for -warnunchecked in user properties file.
#	Content
1	package java.util;
2
3	/**
4	* AbstractQueue provides default implementations of add, remove, and
5	* element based on offer, poll, and peek, respectively but that throw
6	* exceptions instead of indicating failure via false or null returns.
7	* The provided implementations all assume that the base implementation
8	* does <em>not</em> allow null elements.
9	*/
10	public abstract class AbstractQueue<E> extends AbstractCollection<E> implements Queue<E> {
11
12	public boolean add(E x) {
13	if (offer(x))
14	return true;
15	else
16	throw new IllegalStateException("Queue full");
17	}
18
19	public E remove() {
20	E x = poll();
21	if (x != null)
22	return x;
23	else
24	throw new NoSuchElementException();
25	}
26
27	public E element() {
28	E x = peek();
29	if (x != null)
30	return x;
31	else
32	throw new NoSuchElementException();
33	}
34
35	public void clear() {
36	while (poll() != null)
37	;
38	}
39
40	}