1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 18 package org.apache.commons.math.fraction; 19 20 import java.io.Serializable; 21 22 import org.apache.commons.math.Field; 23 24 /** 25 * Representation of the fractional numbers field. 26 * <p> 27 * This class is a singleton. 28 * </p> 29 * @see Fraction 30 * @version $Revision: 795909 $ $Date: 2009-07-20 12:45:08 -0400 (Mon, 20 Jul 2009) $ 31 * @since 2.0 32 */ 33 public class FractionField implements Field<Fraction>, Serializable { 34 35 /** Serializable version identifier */ 36 private static final long serialVersionUID = -1257768487499119313L; 37 38 /** Private constructor for the singleton. 39 */ 40 private FractionField() { 41 } 42 43 /** Get the unique instance. 44 * @return the unique instance 45 */ 46 public static FractionField getInstance() { 47 return LazyHolder.INSTANCE; 48 } 49 50 /** {@inheritDoc} */ 51 public Fraction getOne() { 52 return Fraction.ONE; 53 } 54 55 /** {@inheritDoc} */ 56 public Fraction getZero() { 57 return Fraction.ZERO; 58 } 59 60 /** Holder for the instance. 61 * <p>We use here the Initialization On Demand Holder Idiom.</p> 62 */ 63 private static class LazyHolder { 64 /** Cached field instance. */ 65 private static final FractionField INSTANCE = new FractionField(); 66 } 67 68 /** Handle deserialization of the singleton. 69 * @return the singleton instance 70 */ 71 private Object readResolve() { 72 // return the singleton instance 73 return LazyHolder.INSTANCE; 74 } 75 76 }