content: /**
   * 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 com.aliyun.odps.mapred.example.local.lib.aggregate;
  
  import java.util.ArrayList;
  import java.util.Iterator;
  import java.util.Set;
  import java.util.TreeMap;
  
  /**
   * This class implements a value aggregator that dedupes a sequence of objects.
   */
  public class UniqValueCount implements ValueAggregator {
  
    private TreeMap<Object, Object> uniqItems = null;
  
    private long numItems = 0;
  
    private long maxNumItems = Long.MAX_VALUE;
  
    /**
     * the default constructor
     */
    public UniqValueCount() {
      this(Long.MAX_VALUE);
    }
  
    /**
     * constructor
     *
     * @param maxNum
     *     the limit in the number of unique values to keep.
     */
    public UniqValueCount(long maxNum) {
      uniqItems = new TreeMap<Object, Object>();
      this.numItems = 0;
      maxNumItems = Long.MAX_VALUE;
      if (maxNum > 0) {
        this.maxNumItems = maxNum;
      }
    }
  
    /**
     * Set the limit on the number of unique values
     *
     * @param n
     *     the desired limit on the number of unique values
     * @return the new limit on the number of unique values
     */
    public long setMaxItems(long n) {
      if (n >= numItems) {
        this.maxNumItems = n;
      } else if (this.maxNumItems >= this.numItems) {
        this.maxNumItems = this.numItems;
      }
      return this.maxNumItems;
    }
  
    /**
     * add a value to the aggregator
     *
     * @param val
     *     an object.
     */
    public void addNextValue(Object val) {
      if (this.numItems <= this.maxNumItems) {
        uniqItems.put(val.toString(), "1");
        this.numItems = this.uniqItems.size();
      }
    }
  
    /**
     * @return return the number of unique objects aggregated
     */
    public String getReport() {
      return "" + uniqItems.size();
    }
  
    /**
     * @return the set of the unique objects
     */
    public Set getUniqueItems() {
      return uniqItems.keySet();
    }
  
    /**
     * reset the aggregator
     */
    public void reset() {
      uniqItems = new TreeMap<Object, Object>();
    }
  
    /**
     * @return return an array of the unique objects. The return value is expected
     * to be used by the a combiner.
     */
    public ArrayList getCombinerOutput() {
      Object key = null;
      Iterator iter = uniqItems.keySet().iterator();
      ArrayList<Object> retv = new ArrayList<Object>();
  
      while (iter.hasNext()) {
        key = iter.next();
        retv.add(key);
      }
      return retv;
    }
  }
  