LabelAlphabet.java

/* Copyright (C) 2002 Univ. of Massachusetts Amherst, Computer Science Dept.
 This file is part of "MALLET" (MAchine Learning for LanguagE Toolkit).
 http://www.cs.umass.edu/~mccallum/mallet
 This software is provided under the terms of the Common Public License,
 version 1.0, as published by http://www.opensource.org.  For further
 information, see the file `LICENSE' included with this distribution. */

package edu.nd.nina.types;

import java.util.ArrayList;

/**
 * A mapping from arbitrary objects (usually String's) to integers (and
 * corresponding Label objects) and back.
 * 
 * @author Andrew McCallum <a
 *         href="mailto:mccallum@cs.umass.edu">mccallum@cs.umass.edu</a>
 */
public class LabelAlphabet extends Alphabet {
	ArrayList<Label> labels;

	public LabelAlphabet() {
		super();
		this.labels = new ArrayList<Label>();
	}

	public int lookupIndex(Object entry, boolean addIfNotPresent) {
		int index = super.lookupIndex(entry, addIfNotPresent);
		if (index >= labels.size() && addIfNotPresent)
			labels.add(new Label(entry, this, index));
		return index;
	}

	public Label lookupLabel(Object entry, boolean addIfNotPresent) {
		int index = lookupIndex(entry, addIfNotPresent);
		if (index >= 0)
			return (Label) labels.get(index);
		else
			return null;
	}

	public Label lookupLabel(Object entry) {
		return this.lookupLabel(entry, true);
	}

	public Label lookupLabel(int labelIndex) {
		return (Label) labels.get(labelIndex);
	}

}