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Commons Collections example source code file (SynchronizedCollection.java)

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

Java - Commons Collections tags/keywords

collection, collection, illegalargumentexception, illegalargumentexception, io, iterator, object, object, serializable, string, synchronizedcollection, synchronizedcollection, util

The Commons Collections SynchronizedCollection.java source code

/*
 *  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.commons.collections.collection;

import java.io.Serializable;
import java.util.Collection;
import java.util.Iterator;

/**
 * Decorates another <code>Collection to synchronize its behaviour
 * for a multi-threaded environment.
 * <p>
 * Iterators must be manually synchronized:
 * <pre>
 * synchronized (coll) {
 *   Iterator it = coll.iterator();
 *   // do stuff with iterator
 * }
 * </pre>
 * <p>
 * This class is Serializable from Commons Collections 3.1.
 *
 * @since Commons Collections 3.0
 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
 * 
 * @author Stephen Colebourne
 */
public class SynchronizedCollection implements Collection, Serializable {

    /** Serialization version */
    private static final long serialVersionUID = 2412805092710877986L;

    /** The collection to decorate */
    protected final Collection collection;
    /** The object to lock on, needed for List/SortedSet views */
    protected final Object lock;

    /**
     * Factory method to create a synchronized collection.
     * 
     * @param coll  the collection to decorate, must not be null
     * @return a new synchronized collection
     * @throws IllegalArgumentException if collection is null
     */
    public static Collection decorate(Collection coll) {
        return new SynchronizedCollection(coll);
    }
    
    //-----------------------------------------------------------------------
    /**
     * Constructor that wraps (not copies).
     * 
     * @param collection  the collection to decorate, must not be null
     * @throws IllegalArgumentException if the collection is null
     */
    protected SynchronizedCollection(Collection collection) {
        if (collection == null) {
            throw new IllegalArgumentException("Collection must not be null");
        }
        this.collection = collection;
        this.lock = this;
    }

    /**
     * Constructor that wraps (not copies).
     * 
     * @param collection  the collection to decorate, must not be null
     * @param lock  the lock object to use, must not be null
     * @throws IllegalArgumentException if the collection is null
     */
    protected SynchronizedCollection(Collection collection, Object lock) {
        if (collection == null) {
            throw new IllegalArgumentException("Collection must not be null");
        }
        this.collection = collection;
        this.lock = lock;
    }

    //-----------------------------------------------------------------------
    public boolean add(Object object) {
        synchronized (lock) {
            return collection.add(object);
        }
    }

    public boolean addAll(Collection coll) {
        synchronized (lock) {
            return collection.addAll(coll);
        }
    }

    public void clear() {
        synchronized (lock) {
            collection.clear();
        }
    }

    public boolean contains(Object object) {
        synchronized (lock) {
            return collection.contains(object);
        }
    }

    public boolean containsAll(Collection coll) {
        synchronized (lock) {
            return collection.containsAll(coll);
        }
    }

    public boolean isEmpty() {
        synchronized (lock) {
            return collection.isEmpty();
        }
    }

    /**
     * Iterators must be manually synchronized.
     * <pre>
     * synchronized (coll) {
     *   Iterator it = coll.iterator();
     *   // do stuff with iterator
     * }
     * 
     * @return an iterator that must be manually synchronized on the collection
     */
    public Iterator iterator() {
        return collection.iterator();
    }

    public Object[] toArray() {
        synchronized (lock) {
            return collection.toArray();
        }
    }

    public Object[] toArray(Object[] object) {
        synchronized (lock) {
            return collection.toArray(object);
        }
    }

    public boolean remove(Object object) {
        synchronized (lock) {
            return collection.remove(object);
        }
    }

    public boolean removeAll(Collection coll) {
        synchronized (lock) {
            return collection.removeAll(coll);
        }
    }

    public boolean retainAll(Collection coll) {
        synchronized (lock) {
            return collection.retainAll(coll);
        }
    }

    public int size() {
        synchronized (lock) {
            return collection.size();
        }
    }

    public boolean equals(Object object) {
        synchronized (lock) {
            if (object == this) {
                return true;
            }
            return collection.equals(object);
        }
    }

    public int hashCode() {
        synchronized (lock) {
            return collection.hashCode();
        }
    }

    public String toString() {
        synchronized (lock) {
            return collection.toString();
        }
    }

}

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