tool/src/main/java/org/antlr/misc/OrderedHashSet.java

/*
 * [The "BSD license"]
 *  Copyright (c) 2010 Terence Parr
 *  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions
 *  are met:
 *  1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *  3. The name of the author may not be used to endorse or promote products
 *      derived from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 *  IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 *  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 *  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 *  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 *  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 *  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 *  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 *  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 *  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.antlr.misc;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.List;

/** A HashMap that remembers the order that the elements were added.
 *  You can alter the ith element with set(i,value) too :)  Unique list.
 *  I need the replace/set-element-i functionality so I'm subclassing
 *  OrderedHashSet.
 */
public class OrderedHashSet<T> extends LinkedHashSet<T> {
    /** Track the elements as they are added to the set */
    protected List<T> elements = new ArrayList<T>();

    public T get(int i) {
        return elements.get(i);
    }

    /** Replace an existing value with a new value; updates the element
     *  list and the hash table, but not the key as that has not changed.
     */
    public T set(int i, T value) {
        T oldElement = elements.get(i);
        elements.set(i,value); // update list
        super.remove(oldElement); // now update the set: remove/add
        super.add(value);
        return oldElement;
    }

    /** Add a value to list; keep in hashtable for consistency also;
     *  Key is object itself.  Good for say asking if a certain string is in
     *  a list of strings.
     */
	@Override
    public boolean add(T value) {
        boolean result = super.add(value);
		if ( result ) {  // only track if new element not in set
			elements.add(value);
		}
		return result;
    }

	@Override
    public boolean remove(Object o) {
		throw new UnsupportedOperationException();
		/*
		elements.remove(o);
        return super.remove(o);
        */
    }

	@Override
    public void clear() {
        elements.clear();
        super.clear();
    }

    /** Return the List holding list of table elements.  Note that you are
     *  NOT getting a copy so don't write to the list.
     */
    public List<T> elements() {
        return elements;
    }

	@Override
	public Iterator<T> iterator() {
		return elements.iterator();
	}

	@Override
	public Object[] toArray() {
		return elements.toArray();
	}

	@Override
    public int size() {
		/*
		if ( elements.size()!=super.size() ) {
			ErrorManager.internalError("OrderedHashSet: elements and set size differs; "+
									   elements.size()+"!="+super.size());
        }
        */
        return elements.size();
    }

	@Override
    public String toString() {
        return elements.toString();
    }
}