com.google.gwt.emul.java.util.AbstractQueue Maven / Gradle / Ivy
/*
* Copyright 2007 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package java.util;
import static javaemul.internal.InternalPreconditions.checkArgument;
import static javaemul.internal.InternalPreconditions.checkElement;
import static javaemul.internal.InternalPreconditions.checkNotNull;
import static javaemul.internal.InternalPreconditions.checkState;
/**
* Skeletal implementation of the Queue interface. [Sun
* docs]
*
* @param element type.
*/
public abstract class AbstractQueue extends AbstractCollection implements Queue {
// Should not be instantiated directly.
protected AbstractQueue() {
}
@Override
public boolean add(E o) {
checkState(offer(o), "Unable to add element to queue");
return true;
}
@Override
public boolean addAll(Collection c) {
checkNotNull(c);
checkArgument(c != this, "Can't add a queue to itself");
return super.addAll(c);
}
@Override
public void clear() {
while (poll() != null) {
// empty loop
}
}
@Override
public E element() {
E e = peek();
checkElement(e != null, "Queue is empty");
return e;
}
@Override
public E remove() {
E e = poll();
checkElement(e != null, "Queue is empty");
return e;
}
}