    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    }