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          */

    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          */

    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          */

    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

   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

   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      */

   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 }