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.math3.fraction;
019    
020    import java.io.Serializable;
021    
022    import org.apache.commons.math3.Field;
023    import org.apache.commons.math3.FieldElement;
024    
025    /**
026     * Representation of the fractional numbers field.
027     * <p>
028     * This class is a singleton.
029     * </p>
030     * @see Fraction
031     * @version $Id: FractionField.java 1416643 2012-12-03 19:37:14Z tn $
032     * @since 2.0
033     */
034    public class FractionField implements Field<Fraction>, Serializable  {
035    
036        /** Serializable version identifier */
037        private static final long serialVersionUID = -1257768487499119313L;
038    
039        /** Private constructor for the singleton.
040         */
041        private FractionField() {
042        }
043    
044        /** Get the unique instance.
045         * @return the unique instance
046         */
047        public static FractionField getInstance() {
048            return LazyHolder.INSTANCE;
049        }
050    
051        /** {@inheritDoc} */
052        public Fraction getOne() {
053            return Fraction.ONE;
054        }
055    
056        /** {@inheritDoc} */
057        public Fraction getZero() {
058            return Fraction.ZERO;
059        }
060    
061        /** {@inheritDoc} */
062        public Class<? extends FieldElement<Fraction>> getRuntimeClass() {
063            return Fraction.class;
064        }
065        // CHECKSTYLE: stop HideUtilityClassConstructor
066        /** Holder for the instance.
067         * <p>We use here the Initialization On Demand Holder Idiom.</p>
068         */
069        private static class LazyHolder {
070            /** Cached field instance. */
071            private static final FractionField INSTANCE = new FractionField();
072        }
073        // CHECKSTYLE: resume HideUtilityClassConstructor
074    
075        /** Handle deserialization of the singleton.
076         * @return the singleton instance
077         */
078        private Object readResolve() {
079            // return the singleton instance
080            return LazyHolder.INSTANCE;
081        }
082    
083    }