lucene/analysis/common/src/java/org/apache/lucene/analysis/core/TypeTokenFilter.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.lucene.analysis.core;


import java.util.Set;

import org.apache.lucene.analysis.FilteringTokenFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.tokenattributes.TypeAttribute;

/**
 * Removes tokens whose types appear in a set of blocked types from a token stream.
 */
public final class TypeTokenFilter extends FilteringTokenFilter {

  private final Set<String> stopTypes;
  private final TypeAttribute typeAttribute = addAttribute(TypeAttribute.class);
  private final boolean useWhiteList;

  /**
   * Create a new {@link TypeTokenFilter}.
   * @param input        the {@link TokenStream} to consume
   * @param stopTypes    the types to filter
   * @param useWhiteList if true, then tokens whose type is in stopTypes will
   *                     be kept, otherwise they will be filtered out
   */
  public TypeTokenFilter(TokenStream input, Set<String> stopTypes, boolean useWhiteList) {
    super(input);
    this.stopTypes = stopTypes;
    this.useWhiteList = useWhiteList;
  }

  /**
   * Create a new {@link TypeTokenFilter} that filters tokens out
   * (useWhiteList=false).
   */
  public TypeTokenFilter(TokenStream input, Set<String> stopTypes) {
    this(input, stopTypes, false);
  }

  /**
   * By default accept the token if its type is not a stop type.
   * When the useWhiteList parameter is set to true then accept the token if its type is contained in the stopTypes
   */
  @Override
  protected boolean accept() {
    return useWhiteList == stopTypes.contains(typeAttribute.type());
  }
}