1 /* 2 * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 8 * - Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 11 * - Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * - Neither the name of Oracle nor the names of its 16 * contributors may be used to endorse or promote products derived 17 * from this software without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS 20 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, 21 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR 23 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 24 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 25 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 26 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 27 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 28 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 29 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 /** 33 * The sample illustrates rules to resolve conflicts between inheritance 34 * candidates with <b>default methods</b>. There are two simple rules: 35 * <ul> 36 * <li>Class wins. If the superclass has a concrete or abstract declaration of 37 * this method, then it is preferred over all defaults.</li> 38 * <li>Subtype wins. If an interface extends another interface, and both provide 39 * a default, then the more specific interface wins. </li> 40 * </ul> 41 */ 42 public class Inheritance { 43 44 /** 45 * The behavior of an creature that can swim 46 */ 47 public interface Swimable { 48 49 /** 50 * Return string representation of the swim action for a creature that 51 * can swim 52 * 53 * @return string representation of the swim action for a creature 54 * that can swim 55 */ swim()56 default String swim() { 57 return "I can swim."; 58 } 59 } 60 61 /** 62 * The abstract class that overrides {@link #swim} method 63 */ 64 public abstract static class Fish implements Swimable { 65 66 /** 67 * Return string representation of the swim action for a fish 68 * 69 * @return string representation of the swim action for a fish 70 */ 71 @Override swim()72 public String swim() { 73 return this.getClass().getSimpleName() + " swims under water"; 74 } 75 } 76 77 /** 78 * This class is used for the illustration rule of 1. See the source code 79 * of the {@link #main} method. 80 * <pre> 81 * System.out.println(new Tuna().swim()); //"Tuna swims under water" output is suspected here 82 * </pre> 83 */ 84 public static class Tuna extends Fish implements Swimable { 85 } 86 87 /** 88 * The behavior of an creature that can dive: the interface that overrides 89 * {@link #swim} method (subtype of {@link Swimable}) 90 */ 91 public interface Diveable extends Swimable { 92 93 /** 94 * Return string representation of the swim action for a creature that 95 * can dive 96 * 97 * @return string representation of the swim action for a creature 98 * that can dive 99 */ 100 @Override swim()101 default String swim() { 102 return "I can swim on the surface of the water."; 103 } 104 105 /** 106 * Return string representation of the dive action for a creature that 107 * can dive 108 * 109 * @return string representation of the dive action for a creature 110 * that can dive 111 */ dive()112 default String dive() { 113 return "I can dive."; 114 } 115 } 116 117 /** 118 * This class is used for the illustration of rule 2. See the source code 119 * of the {@link #main} method 120 * <pre> 121 * //"I can swim on the surface of the water." output is suspected here 122 * System.out.println(new Duck().swim()); 123 * </pre> 124 */ 125 public static class Duck implements Swimable, Diveable { 126 } 127 128 /** 129 * Illustrate behavior of the classes: {@link Tuna} and {@link Duck} 130 * 131 * @param args command line arguments 132 */ main(final String[] args)133 public static void main(final String[] args) { 134 // Illustrates rule 1. The Fish.swim() implementation wins 135 //"Tuna swims under water" is output 136 System.out.println(new Tuna().swim()); 137 138 // Illustrates rule 2. The Diveable.swim() implementation wins 139 //"I can swim on the surface of the water." is output 140 System.out.println(new Duck().swim()); 141 } 142 } 143