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.complex;
019    
020    import java.io.Serializable;
021    
022    import org.apache.commons.math.Field;
023    
024    /**
025     * Representation of the complex numbers field.
026     * <p>
027     * This class is a singleton.
028     * </p>
029     * @see Complex
030     * @version $Revision: 811827 $ $Date: 2009-09-06 17:32:50 +0200 (dim. 06 sept. 2009) $
031     * @since 2.0
032     */
033    public class ComplexField implements Field<Complex>, Serializable  {
034    
035        /** Serializable version identifier. */
036        private static final long serialVersionUID = -6130362688700788798L;
037    
038        /** Private constructor for the singleton.
039         */
040        private ComplexField() {
041        }
042    
043        /** Get the unique instance.
044         * @return the unique instance
045         */
046        public static ComplexField getInstance() {
047            return LazyHolder.INSTANCE;
048        }
049    
050        /** {@inheritDoc} */
051        public Complex getOne() {
052            return Complex.ONE;
053        }
054    
055        /** {@inheritDoc} */
056        public Complex getZero() {
057            return Complex.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 ComplexField INSTANCE = new ComplexField();
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    }