001/*
002 * Copyright (c) 2007-2016 Concurrent, Inc. All Rights Reserved.
003 *
004 * Project and contact information: http://www.cascading.org/
005 *
006 * This file is part of the Cascading project.
007 *
008 * Licensed under the Apache License, Version 2.0 (the "License");
009 * you may not use this file except in compliance with the License.
010 * You may obtain a copy of the License at
011 *
012 *     http://www.apache.org/licenses/LICENSE-2.0
013 *
014 * Unless required by applicable law or agreed to in writing, software
015 * distributed under the License is distributed on an "AS IS" BASIS,
016 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
017 * See the License for the specific language governing permissions and
018 * limitations under the License.
019 */
020
021package cascading.operation.aggregator;
022
023import java.beans.ConstructorProperties;
024
025import cascading.tuple.Fields;
026
027/**
028 * Class Min is an {@link cascading.operation.Aggregator} that returns the minimum value encountered in the current group.
029 * <p/>
030 * Values are expected to be {@link Comparable} types vs numeric representations and
031 * the {@link Comparable#compareTo(Object)} result is use for min comparison.
032 */
033public class MinValue extends ExtremaValueBase
034  {
035  /** Field FIELD_NAME */
036  public static final String FIELD_NAME = "min";
037
038  /** Constructs a new instance that returns the Min value encountered in the field name "min". */
039  public MinValue()
040    {
041    super( 1, new Fields( FIELD_NAME ) );
042    }
043
044  /**
045   * Constructs a new instance that returns the minimum value encountered in the given fieldDeclaration field name.
046   *
047   * @param fieldDeclaration of type Fields
048   */
049  @ConstructorProperties({"fieldDeclaration"})
050  public MinValue( Fields fieldDeclaration )
051    {
052    super( 1, fieldDeclaration );
053    }
054
055  /**
056   * Constructs a new instance that returns the minimum value encountered in the given fieldDeclaration field name.
057   * Any argument matching an ignoredValue won't be compared.
058   *
059   * @param fieldDeclaration of type Fields
060   * @param ignoreValues     of type Object...
061   */
062  @ConstructorProperties({"fieldDeclaration", "ignoreValues"})
063  public MinValue( Fields fieldDeclaration, Object... ignoreValues )
064    {
065    super( fieldDeclaration, ignoreValues );
066    }
067
068  @Override
069  protected boolean compare( Comparable lhs, Comparable rhs )
070    {
071    return lhs.compareTo( rhs ) > 0;
072    }
073  }