Update a collection using a minimal update strategy and updating the collection in place. - Java java.util

Java examples for java.util:Collection Operation

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Description

Update a collection using a minimal update strategy and updating the collection in place.

Demo Code

/* $Id$/*from  ww w. j  a va2 s .  c om*/
 *****************************************************************************
 * Copyright (c) 2009 Contributors - see below
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *    tfmorris
 *****************************************************************************
 *
 * Some portions of this file was previously release using the BSD License:
 */

// Copyright (c) 2006 The Regents of the University of California. All
// Rights Reserved. Permission to use, copy, modify, and distribute this
// software and its documentation without fee, and without a written
// agreement is hereby granted, provided that the above copyright notice
// and this paragraph appear in all copies. This software program and
// documentation are copyrighted by The Regents of the University of
// California. The software program and documentation are supplied "AS
// IS", without any accompanying services from The Regents. The Regents
// does not warrant that the operation of the program will be
// uninterrupted or error-free. The end-user understands that the program
// was developed for research purposes and is advised not to rely
// exclusively on the program for any reason. IN NO EVENT SHALL THE
// UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT,
// SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING LOST PROFITS,
// ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF
// THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF
// SUCH DAMAGE. THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY
// WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE
// PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND THE UNIVERSITY OF
// CALIFORNIA HAS NO OBLIGATIONS TO PROVIDE MAINTENANCE, SUPPORT,
// UPDATES, ENHANCEMENTS, OR MODIFICATIONS.

//package com.java2s;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;

public class Main {
    public static void main(String[] argv) {
        Collection base = java.util.Arrays.asList("asdf", "java2s.com");
        Collection updates = java.util.Arrays.asList("asdf", "java2s.com");
        update(base, updates);
    }

    /**
     * Update a collection using a minimal update strategy and updating the
     * collection in place. This can be used with the JMI "live" semantic
     * collections to update the model in place. Order of processing is to first
     * remove all obsolete elements from the collection and then add all new
     * elements.
     * 
     * @param base
     *            the base collection to be updated
     * @param updates
     *            desired end state of collection
     */
    static void update(Collection base, Collection updates) {
        if (updates == null) {
            base.clear();
            return;
        }
        Collection toBeRemoved = new ArrayList();
        Collection toBeAdded = new ArrayList();

        Iterator oldIt = base.iterator();
        while (oldIt.hasNext()) {
            Object obj = oldIt.next();
            if (!updates.contains(obj)) {
                toBeRemoved.add(obj);
            }
        }
        Iterator newIt = updates.iterator();
        while (newIt.hasNext()) {
            Object obj = newIt.next();
            if (!base.contains(obj)) {
                toBeAdded.add(obj);
            }
        }

        base.removeAll(toBeRemoved);
        base.addAll(toBeAdded);
    }
}

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