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.geometry.euclidean.twod;
019    
020    import java.io.Serializable;
021    
022    import org.apache.commons.math3.geometry.Space;
023    import org.apache.commons.math3.geometry.euclidean.oned.Euclidean1D;
024    
025    /**
026     * This class implements a three-dimensional space.
027     * @version $Id: Euclidean2D.java 1416643 2012-12-03 19:37:14Z tn $
028     * @since 3.0
029     */
030    public class Euclidean2D implements Serializable, Space {
031    
032        /** Serializable version identifier. */
033        private static final long serialVersionUID = 4793432849757649566L;
034    
035        /** Private constructor for the singleton.
036         */
037        private Euclidean2D() {
038        }
039    
040        /** Get the unique instance.
041         * @return the unique instance
042         */
043        public static Euclidean2D getInstance() {
044            return LazyHolder.INSTANCE;
045        }
046    
047        /** {@inheritDoc} */
048        public int getDimension() {
049            return 2;
050        }
051    
052        /** {@inheritDoc} */
053        public Euclidean1D getSubSpace() {
054            return Euclidean1D.getInstance();
055        }
056    
057        // CHECKSTYLE: stop HideUtilityClassConstructor
058        /** Holder for the instance.
059         * <p>We use here the Initialization On Demand Holder Idiom.</p>
060         */
061        private static class LazyHolder {
062            /** Cached field instance. */
063            private static final Euclidean2D INSTANCE = new Euclidean2D();
064        }
065        // CHECKSTYLE: resume HideUtilityClassConstructor
066    
067        /** Handle deserialization of the singleton.
068         * @return the singleton instance
069         */
070        private Object readResolve() {
071            // return the singleton instance
072            return LazyHolder.INSTANCE;
073        }
074    
075    }