/**
 *#########################################################################
 *
 * A component of the Gatherer application, part of the Greenstone digital
 * library suite from the New Zealand Digital Library Project at the
 * University of Waikato, New Zealand.
 *
 * Author: John Thompson, Greenstone Digital Library, University of Waikato
 *
 * Copyright (C) 1999 New Zealand Digital Library Project
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *########################################################################
 */
package org.greenstone.gatherer.util;
/**************************************************************************************
 * Written:      04/07/03
 * Revised:      
 **************************************************************************************/
/** Like a boolean except with three states, true, false and undecided. */
public class Troolean {
    static final private byte FALSE     =  0;
    static final private byte TRUE      =  1;
    static final private byte UNDECIDED = -1;

    private byte state = UNDECIDED;

    public Troolean() {
    }

    public Troolean(boolean state) {
	set(state);
    }

    public boolean isDecided() {
	return (state != UNDECIDED);
    }

    public boolean isFalse() {
	return (state == FALSE);
    }

    public boolean isTrue() {
	return (state == TRUE);
    }

    public void reset() {
	state = UNDECIDED;
    }

    public void set(boolean state) {
	if(state) {
	    this.state = TRUE;
	}
	else {
	    this.state = FALSE;
	}
    }
}