com.phoenixst.collections.FilteredCollection.java Source code

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Here is the source code for com.phoenixst.collections.FilteredCollection.java

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/*
 *  $Id: FilteredCollection.java,v 1.11 2006/06/07 18:31:16 rconner Exp $
 *
 *  Copyright (C) 1994-2006 by Phoenix Software Technologists,
 *  Inc. and others.  All rights reserved.
 *
 *  THIS PROGRAM AND DOCUMENTATION IS PROVIDED UNDER THE TERMS OF THE
 *  COMMON PUBLIC LICENSE ("AGREEMENT") WHICH ACCOMPANIES IT.  ANY
 *  USE, REPRODUCTION OR DISTRIBUTION OF THE PROGRAM CONSTITUTES
 *  RECIPIENT'S ACCEPTANCE OF THE AGREEMENT.
 *
 *  The license text can also be found at
 *    http://opensource.org/licenses/cpl.php
 */

package com.phoenixst.collections;

import java.io.*;
import java.util.*;

import org.apache.commons.collections.Predicate;

/**
 *  A <code>Collection</code> which presents a filtered view of
 *  another.
 *
 *  @version    $Revision: 1.11 $
 *  @author     Ray A. Conner
 *
 *  @since      1.0
 */
public class FilteredCollection extends AbstractCollection implements Serializable {

    private static final long serialVersionUID = 3L;

    /**
     *  The wrapped collection.
     *
     *  @serial
     */
    private final Collection delegate;

    /**
     *  The filtering predicate.
     *
     *  @serial
     */
    private final Predicate predicate;

    ////////////////////////////////////////
    // Constructors
    ////////////////////////////////////////

    /**
     *  Creates a new <code>FilteredCollection</code>.  If a
     *  <code>null</code> <code>Predicate</code> is passed to this
     *  constructor, {@link TruePredicate} is used internally.
     */
    public FilteredCollection(Collection delegate, Predicate predicate) {
        super();
        this.delegate = delegate;
        this.predicate = (predicate != null) ? predicate : TruePredicate.INSTANCE;
        if (delegate == null) {
            throw new IllegalArgumentException("Wrapped Collection is null.");
        }
    }

    ////////////////////////////////////////
    // Serialization methods
    ////////////////////////////////////////

    private void readObject(ObjectInputStream in) throws ClassNotFoundException, IOException {
        in.defaultReadObject();
        if (delegate == null) {
            throw new InvalidObjectException("Wrapped Collection is null.");
        }
        if (predicate == null) {
            throw new InvalidObjectException("Predicate is null.");
        }
    }

    ////////////////////////////////////////
    // Collection
    ////////////////////////////////////////

    public int size() {
        int size = 0;
        for (Iterator i = delegate.iterator(); i.hasNext();) {
            if (predicate.evaluate(i.next())) {
                size++;
            }
        }
        return size;
    }

    public boolean isEmpty() {
        for (Iterator i = delegate.iterator(); i.hasNext();) {
            if (predicate.evaluate(i.next())) {
                return false;
            }
        }
        return true;
    }

    public boolean add(Object object) {
        if (!predicate.evaluate(object)) {
            throw new IllegalArgumentException("Element " + object + " does not satisfy predicate " + predicate);
        }
        return delegate.add(object);
    }

    public boolean remove(Object object) {
        return predicate.evaluate(object) && delegate.remove(object);
    }

    public boolean contains(Object object) {
        return predicate.evaluate(object) && delegate.contains(object);
    }

    /**
     *  Returns an <code>Iterator</code> over the elements of this
     *  <code>Collection</code>.  If the <code>remove()</code> method
     *  is called after <code>hasNext()</code> without an intervening
     *  call to <code>next()</code>, the last element returned by
     *  <code>next()</code> will be removed by calling {@link
     *  Collection#remove Collection.remove( object )} on the
     *  underlying <code>Collection</code>.  Depending upon the
     *  underlying <code>Collection</code> implementation, this may
     *  invalidate this <code>Iterator</code>.
     */
    public Iterator iterator() {
        return new IteratorImpl(delegate, predicate);
    }

    ////////////////////////////////////////
    // Private classes
    ////////////////////////////////////////

    /**
     *  Protected iterator implementation.
     */
    private static class IteratorImpl extends FilteredIterator {
        private final Collection delegate;

        IteratorImpl(Collection delegate, Predicate predicate) {
            super(delegate.iterator(), predicate);
            this.delegate = delegate;
        }

        protected void remove(Object object) {
            delegate.remove(object);
        }
    }

}