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Java example source code file (RWMap.java)

This example Java source code file (RWMap.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

collection, not, nullpointerexception, object, reentrantreadwritelock, rwmap, set, string, threading, threads, treemap, util

The RWMap.java Java example source code

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

/*
 * This file is available under and governed by the GNU General Public
 * License version 2 only, as published by the Free Software Foundation.
 * However, the following notice accompanied the original version of this
 * file:
 *
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 */

import java.util.*;
import java.util.concurrent.*;
import java.util.concurrent.locks.*;


/**
 * This is an incomplete implementation of a wrapper class
 * that places read-write locks around unsynchronized Maps.
 * Exists as a sample input for MapLoops test.
 */

public class RWMap implements Map {
    private final Map m;
    private final ReentrantReadWriteLock rwl = new ReentrantReadWriteLock();

    public RWMap(Map m) {
        if (m == null)
            throw new NullPointerException();
        this.m = m;
    }

    public RWMap() {
        this(new TreeMap()); // use TreeMap by default
    }

    public int size() {
        rwl.readLock().lock();
        try { return m.size(); }
        finally { rwl.readLock().unlock(); }
    }

    public boolean isEmpty() {
        rwl.readLock().lock();
        try { return m.isEmpty(); }
        finally { rwl.readLock().unlock(); }
    }

    public Object get(Object key) {
        rwl.readLock().lock();
        try { return m.get(key); }
        finally { rwl.readLock().unlock(); }
    }

    public boolean containsKey(Object key) {
        rwl.readLock().lock();
        try { return m.containsKey(key); }
        finally { rwl.readLock().unlock(); }
    }

    public boolean containsValue(Object value) {
        rwl.readLock().lock();
        try { return m.containsValue(value); }
        finally { rwl.readLock().unlock(); }
    }


    public Set keySet() { // Not implemented
        return null;
    }

    public Set entrySet() { // Not implemented
        return null;
    }

    public Collection values() { // Not implemented
        return null;
    }

    public boolean equals(Object o) {
        rwl.readLock().lock();
        try { return m.equals(o); }
        finally { rwl.readLock().unlock(); }
    }

    public int hashCode() {
        rwl.readLock().lock();
        try { return m.hashCode(); }
        finally { rwl.readLock().unlock(); }
    }

    public String toString() {
        rwl.readLock().lock();
        try { return m.toString(); }
        finally { rwl.readLock().unlock(); }
    }

    public Object put(Object key, Object value) {
        rwl.writeLock().lock();
        try { return m.put(key, value); }
        finally { rwl.writeLock().unlock(); }
    }

    public Object remove(Object key) {
        rwl.writeLock().lock();
        try { return m.remove(key); }
        finally { rwl.writeLock().unlock(); }
    }

    public void putAll(Map map) {
        rwl.writeLock().lock();
        try { m.putAll(map); }
        finally { rwl.writeLock().unlock(); }
    }

    public void clear() {
        rwl.writeLock().lock();
        try { m.clear(); }
        finally { rwl.writeLock().unlock(); }
    }

}

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