package it.unimi.dsi.mg4j.query.nodes;import java.util.Arrays;import it.unimi.dsi.fastutil.objects.ObjectOpenHashSet;import it.unimi.dsi.mg4j.index.MultiTermIndexIterator;import it.unimi.dsi.mg4j.search.DocumentIterator;import it.unimi.dsi.lang.MutableString;/*		  * MG4J: Managing Gigabytes for Java * * Copyright (C) 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. * *//** A node representing a virtual term obtained by merging the occurrences of the given terms. *  * <p>This node is mainly useful when performing query expansion. The {@link QueryBuilderVisitor} * used to generate {@linkplain DocumentIterator document iterators} can decide which * policy to use for setting the frequency and the name of the virtual term. *  * @author Sebastiano Vigna * @see MultiTermIndexIterator */public class MultiTerm extends Composite {		/** Creates a new multi-term node.	 * 	 * @param term a vector of nodes representing distinct terms.	 * @throws IllegalArgumentException if some term appears twice in <code>term</code>.	 */		@SuppressWarnings("cast")	public MultiTerm( final Term... term ) {		super( (Query[])term );		final ObjectOpenHashSet<MutableString> s = new ObjectOpenHashSet<MutableString>( term.length );		for( Term t : term ) s.add( new MutableString( t.term ) );		if ( s.size() != term.length ) throw new IllegalArgumentException( "Multiterm nodes require distinct terms" );	}	public String toString() {		return super.toString( "MULTITERM(", ")", ", " );	}	public <T> T accept( final QueryBuilderVisitor<T> visitor ) throws QueryBuilderVisitorException {		if ( ! visitor.visitPre( this ) ) return null;		final T[] result = visitor.newArray( query.length );		for( int i = 0; i < query.length; i++ ) if ( ( result[ i ] = query[ i ].accept( visitor ) ) == null ) return null;		return visitor.visitPost( this, result );	}	public boolean equals( final Object o ) {		if ( ! ( o instanceof MultiTerm ) ) return false;		return Arrays.equals( query, ((MultiTerm)o).query );	}		public int hashCode() {		return Arrays.hashCode( query ) ^ getClass().hashCode();	}}