not.java

MG4J (Managing Gigabytes for Java) is a free full-text search engine for large document collections

package it.unimi.dsi.mg4j.query.nodes;

/*		 
 * MG4J: Managing Gigabytes for Java
 *
 * Copyright (C) 2006-2007 Sebastiano Vigna 
 *
 *  This library is free software; you can redistribute it and/or modify it
 *  under the terms of the GNU Lesser General Public License as published by the Free
 *  Software Foundation; either version 2.1 of the License, or (at your option)
 *  any later version.
 *
 *  This library 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 Lesser General Public License
 *  for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 */

import it.unimi.dsi.lang.MutableString;

/** A node representing the logical not of the underlying query.
 *  
 * @author Sebastiano Vigna
 */

public class Not implements Query {
	/** The only underlying node. */
	public final Query query;

	public Not( final Query query ) {
		this.query = query;
	}
	
	public String toString() {
		return new MutableString().append( "! (" ).append( query ).append( ')' ).toString();
	}

	public <T> T accept( final QueryBuilderVisitor<T> visitor ) throws QueryBuilderVisitorException {
		if ( ! visitor.visitPre( this ) ) return null;
		final T result = query.accept( visitor );
		if ( result == null ) return null;
		return visitor.visitPost( this, result );
	}

	public boolean equals( final Object o ) {
		if ( ! ( o instanceof Not) ) return false;
		return query.equals( ((Not)o).query );
	}
	
	public int hashCode() {
		return ~query.hashCode();
	}
}