LinkedHashSetCollectionFactory.java :  » Database-ORM » ODAL » com » completex » objective » components » persistency » type » Java Open Source

/**
 *  Objective Database Abstraction Layer (ODAL)
 *  Copyright (c) 2004, The ODAL Development Group
 *  All rights reserved.
 *  For definition of the ODAL Development Group please refer to LICENCE.txt file
 *
 *  Distributable under LGPL license.
 *  See terms of license at gnu.org.
 */
package com.completex.objective.components.persistency.type;

import java.util.Collection;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.NoSuchElementException;

/**
 * @author Gennady Krizhevsky
 */
public class LinkedHashSetCollectionFactory extends AbstractSetCollectionFactory implements CollectionFactory {

    public static final NullLinkedHashSetFactory NULL_LINKED_HASH_SET_FACTORY = new NullLinkedHashSetFactory();

    public Collection newCollection() {
        return new LinkedHashSet();
    }

    private static final LinkedHashSetCollectionFactory FACTORY = new LinkedHashSetCollectionFactory();

    public static LinkedHashSetCollectionFactory factory() {
        return FACTORY;
    }


    public CollectionFactory nullCollectionFactory() {
        return NULL_LINKED_HASH_SET_FACTORY;
    }

    private static class NullLinkedHashSetFactory implements CollectionFactory {
        public Collection newCollection() {
            return NULL_LINKED_HASH_SET;
        }

        public CollectionFactory nullCollectionFactory() {
            return this;
        }
    }

    public static final NullLinkedHashSet NULL_LINKED_HASH_SET = new NullLinkedHashSet();

    private static class NullLinkedHashSet extends LinkedHashSet {

        public NullLinkedHashSet() {
        }

        public NullLinkedHashSet(Collection collection) {
        }

        public NullLinkedHashSet(int initialCapacity, float loadFactor) {
        }

        public NullLinkedHashSet(int initialCapacity) {
        }

        public Iterator iterator() {
            return new Iterator() {
                public boolean hasNext() {
                    return false;
                }

                public Object next() {
                    throw new NoSuchElementException();
                }

                public void remove() {
                    throw new UnsupportedOperationException();
                }
            };
        }

        public int size() {
            return 0;
        }

        public boolean contains(Object obj) {
            return false;
        }

        // Preserves singleton property
        private Object readResolve() {
            return NULL_LINKED_HASH_SET;
        }

        public boolean add(Object o) {
            return false;
        }
    }

    public static void main(String[] args) {
        NULL_LINKED_HASH_SET.remove("");
    }

}