/*
* Copyright 2015 MovingBlocks
*
* 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 org.terasology.util.collection;
import com.google.common.collect.Iterators;
import com.google.common.collect.Queues;
import com.google.common.collect.Sets;
import java.util.Collection;
import java.util.Iterator;
import java.util.Queue;
import java.util.Set;
/**
* A queue that ensures its contents are unique - an attempt to add an element to the queue that is already in the queue will be ignored.
*
* @author Immortius
*/
public class UniqueQueue<T> implements Queue<T> {
private final Set<T> containedSet;
private final Queue<T> internalQueue;
/**
* Creates a new, empty queue
*/
public UniqueQueue() {
this(Sets.<T>newHashSet(), Queues.<T>newArrayDeque());
}
private UniqueQueue(Set<T> internalSet, Queue<T> internalQueue) {
this.containedSet = internalSet;
this.internalQueue = internalQueue;
}
/**
* @param <T> The type that can be contained in the queue
* @return A new, empty queue
*/
public static <T> UniqueQueue<T> create() {
return new UniqueQueue<>();
}
/**
* @param size The expected size of the queue
* @param <T> The type that can be contained in the queue
* @return A new, empty queue.
*/
public static <T> UniqueQueue<T> createWithExpectedSize(int size) {
return new UniqueQueue<>(Sets.<T>newHashSetWithExpectedSize(size), Queues.<T>newArrayDeque());
}
@Override
public int size() {
return containedSet.size();
}
@Override
public boolean isEmpty() {
return containedSet.isEmpty();
}
@Override
public boolean contains(Object o) {
return containedSet.contains(o);
}
@Override
public Iterator<T> iterator() {
return Iterators.unmodifiableIterator(internalQueue.iterator());
}
@Override
public Object[] toArray() {
return internalQueue.toArray();
}
@Override
public <U> U[] toArray(U[] a) {
return internalQueue.toArray(a);
}
@Override
public boolean add(T t) {
return containedSet.add(t) && internalQueue.add(t);
}
@Override
public boolean remove(Object o) {
return containedSet.remove(o) && internalQueue.remove(o);
}
@Override
public boolean containsAll(Collection<?> c) {
return containedSet.containsAll(c);
}
@Override
public boolean addAll(Collection<? extends T> c) {
boolean changed = false;
for (T item : c) {
if (containedSet.add(item)) {
internalQueue.add(item);
changed = true;
}
}
return changed;
}
@Override
public boolean removeAll(Collection<?> c) {
return containedSet.removeAll(c) && internalQueue.removeAll(c);
}
@Override
public boolean retainAll(Collection<?> c) {
return containedSet.retainAll(c) && internalQueue.retainAll(c);
}
@Override
public void clear() {
containedSet.clear();
internalQueue.clear();
}
@Override
public boolean offer(T t) {
return containedSet.add(t) && internalQueue.offer(t);
}
@Override
public T remove() {
T result = internalQueue.remove();
containedSet.remove(result);
return result;
}
@Override
public T poll() {
T result = internalQueue.poll();
containedSet.remove(result);
return result;
}
@Override
public T element() {
return internalQueue.element();
}
@Override
public T peek() {
return internalQueue.peek();
}
}