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.
#	User	Rev	Content
1	tim	1.1	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			}