/* * * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you 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.apache.hadoop.hbase.util; import java.util.Collection; import java.util.Comparator; import java.util.Iterator; import java.util.SortedSet; import java.util.TreeSet; import org.apache.hadoop.classification.InterfaceAudience; import org.apache.hadoop.classification.InterfaceStability; /** * Simple {@link java.util.SortedSet} implementation that uses an internal * {@link java.util.TreeSet} to provide ordering. All mutation operations * create a new copy of the <code>TreeSet</code> instance, so are very * expensive. This class is only intended for use on small, very rarely * written collections that expect highly concurrent reads. Read operations * are performed on a reference to the internal <code>TreeSet</code> at the * time of invocation, so will not see any mutations to the collection during * their operation. * * <p>Note that due to the use of a {@link java.util.TreeSet} internally, * a {@link java.util.Comparator} instance must be provided, or collection * elements must implement {@link java.lang.Comparable}. * </p> * @param <E> A class implementing {@link java.lang.Comparable} or able to be * compared by a provided comparator. */ @InterfaceAudience.Public @InterfaceStability.Stable public class SortedCopyOnWriteSet<E> implements SortedSet<E> { private volatile SortedSet<E> internalSet; public SortedCopyOnWriteSet() { this.internalSet = new TreeSet<E>(); } public SortedCopyOnWriteSet(Collection<? extends E> c) { this.internalSet = new TreeSet<E>(c); } public SortedCopyOnWriteSet(Comparator<? super E> comparator) { this.internalSet = new TreeSet<E>(comparator); } @Override public int size() { return internalSet.size(); } @Override public boolean isEmpty() { return internalSet.isEmpty(); } @Override public boolean contains(Object o) { return internalSet.contains(o); } @Override public Iterator<E> iterator() { return internalSet.iterator(); } @Override public Object[] toArray() { return internalSet.toArray(); } @Override public <T> T[] toArray(T[] a) { return internalSet.toArray(a); } @Override public synchronized boolean add(E e) { SortedSet<E> newSet = new TreeSet<E>(internalSet); boolean added = newSet.add(e); internalSet = newSet; return added; } @Override public synchronized boolean remove(Object o) { SortedSet<E> newSet = new TreeSet<E>(internalSet); boolean removed = newSet.remove(o); internalSet = newSet; return removed; } @Override public boolean containsAll(Collection<?> c) { return internalSet.containsAll(c); } @Override public synchronized boolean addAll(Collection<? extends E> c) { SortedSet<E> newSet = new TreeSet<E>(internalSet); boolean changed = newSet.addAll(c); internalSet = newSet; return changed; } @Override public synchronized boolean retainAll(Collection<?> c) { SortedSet<E> newSet = new TreeSet<E>(internalSet); boolean changed = newSet.retainAll(c); internalSet = newSet; return changed; } @Override public synchronized boolean removeAll(Collection<?> c) { SortedSet<E> newSet = new TreeSet<E>(internalSet); boolean changed = newSet.removeAll(c); internalSet = newSet; return changed; } @Override public synchronized void clear() { Comparator<? super E> comparator = internalSet.comparator(); if (comparator != null) { internalSet = new TreeSet<E>(comparator); } else { internalSet = new TreeSet<E>(); } } @Override public Comparator<? super E> comparator() { return internalSet.comparator(); } @Override public SortedSet<E> subSet(E fromElement, E toElement) { return internalSet.subSet(fromElement, toElement); } @Override public SortedSet<E> headSet(E toElement) { return internalSet.headSet(toElement); } @Override public SortedSet<E> tailSet(E fromElement) { return internalSet.tailSet(fromElement); } @Override public E first() { return internalSet.first(); } @Override public E last() { return internalSet.last(); } }