OnJava8-Examples/generics/LatentReflection.java

// generics/LatentReflection.java
// (c)2021 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
// Using reflection for latent typing
import java.lang.reflect.*;

// Does not implement Performs:
class Mime {
  public void walkAgainstTheWind() {}
  public void sit() {
    System.out.println("Pretending to sit");
  }
  public void pushInvisibleWalls() {}
  @Override public String toString() { return "Mime"; }
}

// Does not implement Performs:
class SmartDog {
  public void speak() { System.out.println("Woof!"); }
  public void sit() { System.out.println("Sitting"); }
  public void reproduce() {}
}

class CommunicateReflectively {
  public static void perform(Object speaker) {
    Class<?> spkr = speaker.getClass();
    try {
      try {
        Method speak = spkr.getMethod("speak");
        speak.invoke(speaker);
      } catch(NoSuchMethodException e) {
        System.out.println(speaker + " cannot speak");
      }
      try {
        Method sit = spkr.getMethod("sit");
        sit.invoke(speaker);
      } catch(NoSuchMethodException e) {
        System.out.println(speaker + " cannot sit");
      }
    } catch(SecurityException |
            IllegalAccessException |
            IllegalArgumentException |
            InvocationTargetException e) {
      throw new RuntimeException(speaker.toString(), e);
    }
  }
}

public class LatentReflection {
  public static void main(String[] args) {
    CommunicateReflectively.perform(new SmartDog());
    CommunicateReflectively.perform(new Robot());
    CommunicateReflectively.perform(new Mime());
  }
}
/* Output:
Woof!
Sitting
Click!
Clank!
Mime cannot speak
Pretending to sit
*/