/* * 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; /** * This class provides skeletal implementations of some {@link Queue} * operations. The implementations in this class are appropriate when * the base implementation does not allow null * elements. Methods {@link #add add}, {@link #remove remove}, and * {@link #element element} are based on {@link #offer offer}, {@link * #poll poll}, and {@link #peek peek}, respectively but throw * exceptions instead of indicating failure via false or * null returns. * *
A Queue implementation that extends this class must
* minimally define a method {@link Queue#offer} which does not permit
* insertion of null elements, along with methods {@link
* Queue#peek}, {@link Queue#poll}, {@link Collection#size}, and a
* {@link Collection#iterator} supporting {@link
* Iterator#remove}. Typically, additional methods will be overridden
* as well. If these requirements cannot be met, consider instead
* subclassing {@link AbstractCollection}.
*
* @since 1.5
* @author Doug Lea
* @param This implementation repeatedly invokes {@link #poll poll} until it
* returns null.
*/
public void clear() {
while (poll() != null)
;
}
/**
* Adds all of the elements in the specified collection to this
* queue. Attempts to addAll of a queue to itself result in
* IllegalArgumentException. Further, the behavior of
* this operation is undefined if the specified collection is
* modified while the operation is in progress.
*
* This implementation iterates over the specified collection,
* and adds each element returned by the iterator to this
* collection, in turn. A runtime exception encountered while
* trying to add an element (including, in particular, a
* null element) may result in only some of the elements
* having been successfully added when the associated exception is
* thrown.
*
* @param c collection whose elements are to be added to this collection.
* @return true if this collection changed as a result of the
* call.
* @throws NullPointerException if the specified collection or
* any of its elements are null.
* @throws IllegalArgumentException if c is this queue.
*
* @see #add(Object)
*/
public boolean addAll(Collection extends E> c) {
if (c == null)
throw new NullPointerException();
if (c == this)
throw new IllegalArgumentException();
boolean modified = false;
Iterator extends E> e = c.iterator();
while (e.hasNext()) {
if (add(e.next()))
modified = true;
}
return modified;
}
}