https://lucene.apache.org/lucene-parent/lucene-core: Apache Lucene Java Core (The Apache Software Foundation) 
/*
 * 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,
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 * See the License for the specific language governing permissions and
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package org.apache.lucene.index;

import java.io.IOException;


A per-document numeric value.

/**
 * A per-document numeric value.
 */
public abstract class NumericDocValues extends DocValuesIterator {
  
  
Sole constructor. (For invocation by subclass 
 constructors, typically implicit.) 
/** Sole constructor. (For invocation by subclass 
   *  constructors, typically implicit.) */
  protected NumericDocValues() {}

  
Returns the numeric value for the current document ID. It is illegal to call this method after DocValuesIterator.advanceExact(int) returned false. 
Returns:numeric value
/**
   * Returns the numeric value for the current document ID.
   * It is illegal to call this method after {@link #advanceExact(int)}
   * returned {@code false}.
   * @return numeric value
   */
  public abstract long longValue() throws IOException;

}