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 import java.lang.reflect.InvocationTargetException; 33 import java.lang.reflect.Method; 34 import java.util.Arrays; 35 import java.util.stream.Stream; 36 37 /** 38 * The code sample illustrates changes in the reflection API linked 39 * <b>default methods</b>. Since Java SE 8, a new method is added into the class 40 * <b><code>java.lang.reflect.Method</code></b>, with which you can reflectively 41 * determine whether or not a default method provided by an interface 42 * (<b><code>Method.isDefault()</code></b>). 43 */ 44 public class Reflection { 45 46 /** 47 * Base interface to illustrate the new reflection API. 48 * 49 * @see Dog 50 */ 51 public interface Animal { 52 53 /** 54 * Return string representation of the eat action for Animal 55 * 56 * @return string representation of the eat action for Animal 57 */ eat()58 default String eat() { 59 return this.getClass().getSimpleName() 60 + " eats like an ordinary animal"; 61 } 62 63 /** 64 * Return string representation of the sleep action for Animal 65 * 66 * @return string representation of the sleep action for Animal 67 */ sleep()68 default String sleep() { 69 return this.getClass().getSimpleName() 70 + " sleeps like an ordinary animal"; 71 } 72 73 /** 74 * Return string representation of the go action for Animal 75 * 76 * @return string representation of the go action for Animal 77 */ go()78 String go(); 79 } 80 81 /** 82 * Dog class to illustrate the new reflection API. You can see that: 83 * <ul> 84 * <li> the {@link #go} and {@link #sleep} methods are not default. 85 * {@link #go} is not the default implementation and the {@link #sleep} 86 * method implementation wins as subtype (according with {@link Inheritance} 87 * rule. 2) </li> 88 * <li> the {@link #eat} is a simple default method that is not overridden 89 * in this class. 90 * </li> 91 * </ul> 92 */ 93 public static class Dog implements Animal { 94 95 /** 96 * Return string representation of the go action for Dog 97 * 98 * @return string representation of the go action for Dog 99 */ 100 @Override go()101 public String go() { 102 return "Dog walks on four legs"; 103 } 104 105 /** 106 * Return string representation of the sleep action for Dog 107 * 108 * @return string representation of the sleep action for Dog 109 */ 110 @Override sleep()111 public String sleep() { 112 return "Dog sleeps"; 113 } 114 } 115 116 /** 117 * Illustrate the usage of the method java.lang.reflect.Method.isDefault() 118 * 119 * @param args command-line arguments 120 * @throws NoSuchMethodException internal demo error 121 */ main(final String[] args)122 public static void main(final String[] args) throws NoSuchMethodException { 123 Dog dog = new Dog(); 124 Stream.of(Dog.class.getMethod("eat"), Dog.class.getMethod("go"), Dog.class.getMethod("sleep")) 125 .forEach((m) -> { 126 System.out.println("Method name: " + m.getName()); 127 System.out.println(" isDefault: " + m.isDefault()); 128 System.out.print(" invoke: "); 129 try { 130 m.invoke(dog); 131 } catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException ex) { 132 } 133 System.out.println(); 134 }); 135 } 136 } 137