| /* |
| |
| Derby - Class org.apache.derbyTesting.functionTests.tests.lang.ModeAggregate |
| |
| 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.derbyTesting.functionTests.tests.lang; |
| |
| import java.io.Serializable; |
| import java.util.Arrays; |
| import java.util.Collections; |
| import java.util.HashMap; |
| |
| import org.apache.derby.agg.Aggregator; |
| |
| /** |
| * <p> |
| * This is a mode aggregator for ints. |
| * </p> |
| */ |
| public class ModeAggregate implements Aggregator<Integer,Integer,ModeAggregate> |
| { |
| /////////////////////////////////////////////////////////////////////////////////// |
| // |
| // STATE |
| // |
| /////////////////////////////////////////////////////////////////////////////////// |
| |
| private HashMap<Integer,Accumulator> _accumulators; |
| |
| /////////////////////////////////////////////////////////////////////////////////// |
| // |
| // CONSTRUCTOR |
| // |
| /////////////////////////////////////////////////////////////////////////////////// |
| |
| public ModeAggregate() {} |
| |
| public void init() |
| { |
| _accumulators = new HashMap<Integer,Accumulator>(); |
| } |
| public void accumulate( Integer value ) |
| { |
| getAccumulator( value ).add( 1 ); |
| } |
| public void merge( ModeAggregate otherAggregator ) |
| { |
| HashMap<Integer,Accumulator> otherAccumulators = otherAggregator._accumulators; |
| |
| for ( Integer value : otherAccumulators.keySet() ) |
| { |
| getAccumulator( value ).add( otherAccumulators.get( value ).getCount() ); |
| } |
| } |
| |
| public Integer terminate() |
| { |
| return _accumulators.isEmpty() ? null : Collections.max( _accumulators.values() ).getValue(); |
| } |
| |
| private Accumulator getAccumulator( Integer value ) |
| { |
| Accumulator retval = _accumulators.get( value ); |
| if ( retval == null ) |
| { |
| retval = new Accumulator( value ); |
| _accumulators.put( value, retval ); |
| } |
| |
| return retval; |
| } |
| |
| /////////////////////////////////////////////////////////////////////////////////// |
| // |
| // NESTED CLASSES |
| // |
| /////////////////////////////////////////////////////////////////////////////////// |
| |
| public static final class Accumulator implements Comparable<Accumulator>, Serializable |
| { |
| private Integer _value; |
| private int _count; |
| |
| public Accumulator( Integer value ) |
| { |
| _value = value; |
| _count = 0; |
| } |
| |
| public void add( int increment ) { _count += increment; } |
| |
| public Integer getValue() { return _value; } |
| public int getCount() { return _count; } |
| |
| // Comparable behavior |
| public int compareTo( Accumulator that ) |
| { |
| int retval = this._count - that._count; |
| |
| if ( retval != 0 ) { return retval; } |
| else { return this._value.intValue() - that._value.intValue(); } |
| } |
| } |
| } |