lucene/core/src/java/org/apache/lucene/index/Fields.java

package org.apache.lucene.index;

/**
 * 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.
 */

import java.io.IOException;

/** Flex API for access to fields and terms
 *  @lucene.experimental */

public abstract class Fields {

  /** Returns an iterator that will step through all fields
   *  names.  This will not return null.  */
  public abstract FieldsEnum iterator() throws IOException;

  /** Get the {@link Terms} for this field.  This will return
   *  null if the field does not exist. */
  public abstract Terms terms(String field) throws IOException;

  /** Returns the number of terms for all fields, or -1 if this 
   *  measure isn't stored by the codec. Note that, just like 
   *  other term measures, this measure does not take deleted 
   *  documents into account. */
  public abstract int size() throws IOException;
  
  /** Returns the number of terms for all fields, or -1 if this 
   *  measure isn't stored by the codec. Note that, just like 
   *  other term measures, this measure does not take deleted 
   *  documents into account. */
  // TODO: deprecate?
  public long getUniqueTermCount() throws IOException {
    long numTerms = 0;
    FieldsEnum it = iterator();
    while(true) {
      String field = it.next();
      if (field == null) {
        break;
      }
      Terms terms = terms(field);
      if (terms != null) {
        final long termCount = terms.size();
        if (termCount == -1) {
          return -1;
        }
          
        numTerms += termCount;
      }
    }
    return numTerms;
  }
  
  public final static Fields[] EMPTY_ARRAY = new Fields[0];
}