001 /* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 018 package org.apache.commons.math.fraction; 019 020 import java.io.Serializable; 021 022 import org.apache.commons.math.Field; 023 024 /** 025 * Representation of the fractional numbers field. 026 * <p> 027 * This class is a singleton. 028 * </p> 029 * @see Fraction 030 * @version $Revision: 811827 $ $Date: 2009-09-06 11:32:50 -0400 (Sun, 06 Sep 2009) $ 031 * @since 2.0 032 */ 033 public class FractionField implements Field<Fraction>, Serializable { 034 035 /** Serializable version identifier */ 036 private static final long serialVersionUID = -1257768487499119313L; 037 038 /** Private constructor for the singleton. 039 */ 040 private FractionField() { 041 } 042 043 /** Get the unique instance. 044 * @return the unique instance 045 */ 046 public static FractionField getInstance() { 047 return LazyHolder.INSTANCE; 048 } 049 050 /** {@inheritDoc} */ 051 public Fraction getOne() { 052 return Fraction.ONE; 053 } 054 055 /** {@inheritDoc} */ 056 public Fraction getZero() { 057 return Fraction.ZERO; 058 } 059 060 // CHECKSTYLE: stop HideUtilityClassConstructor 061 /** Holder for the instance. 062 * <p>We use here the Initialization On Demand Holder Idiom.</p> 063 */ 064 private static class LazyHolder { 065 /** Cached field instance. */ 066 private static final FractionField INSTANCE = new FractionField(); 067 } 068 // CHECKSTYLE: resume HideUtilityClassConstructor 069 070 /** Handle deserialization of the singleton. 071 * @return the singleton instance 072 */ 073 private Object readResolve() { 074 // return the singleton instance 075 return LazyHolder.INSTANCE; 076 } 077 078 }