OnJava8-Examples/functional/MethodReferences.java

// functional/MethodReferences.java
// (c)2016 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://mindviewinc.com/Books/OnJava/ for more book information.
import java.util.*;

interface Callable { // (1)
  void call(String s);
}

class Describe {
  void show(String msg) { // (2)
    System.out.println(msg);
  }
}

public class MethodReferences {
  static void hello(String name) { // (3)
    System.out.println("Hello, " + name);
  }
  static class Description {
    String about;
    public Description(String desc) { about = desc; }
    void help(String msg) { // (4)
      System.out.println(about + " " + msg);
    }
  }
  static class Helper {
    static void assist(String msg) { // (5)
      System.out.println(msg);
    }
  }
  public static void main(String[] args) {
    Describe d = new Describe();
    Callable c = d::show; // (6)
    c.call("call()"); // (7)

    c = MethodReferences::hello; // (8)
    c.call("Bob");

    c = new Description("valuable")::help; // (9)
    c.call("information");

    c = Helper::assist; // (10)
    c.call("Help!");
  }
}
/* Output:
call()
Hello, Bob
valuable information
Help!
*/