Java - Lambda Expressions Target Typing

Introduction

Using Lambda Expressions as Method Arguments

Demo

public class Main {
  public static void main(String[] args) {
    LambdaUtil util = new LambdaUtil();

    // Call the testAdder() method
    util.testAdder((x, y) -> x + y);//from w  w  w . j av a 2s .  c om

    // Call the testJoiner() method
    util.testJoiner((x, y) -> x + y);

    // Call the testJoiner() method. The Joiner will
    // add a space between the two strings
    util.testJoiner((x, y) -> x + " " + y);

    // Call the testJoiner() method. The Joiner will
    // reverse the strings and join resulting strings in
    // reverse order adding a comma in between
    util.testJoiner((x, y) -> {
      StringBuilder sbx = new StringBuilder(x);
      StringBuilder sby = new StringBuilder(y);
      sby.reverse().append(",").append(sbx.reverse());
      return sby.toString();
    });
  }
}
@FunctionalInterface
interface Adder {
        double add(double n1, double n2);
}
@FunctionalInterface
interface Joiner {
        String join(String s1, String s2);
}
class LambdaUtil {
  public void testAdder(Adder adder) {
    double x = 190.90;
    double y = 8.50;
    double sum = adder.add(x, y);
    System.out.print("Using an Adder:");
    System.out.println(x + " + " + y + " = " + sum);
  }

  public void testJoiner(Joiner joiner) {
    String s1 = "Hello";
    String s2 = "World";
    String s3 = joiner.join(s1, s2);
    System.out.print("Using a Joiner:");
    System.out.println("\"" + s1 + "\" + \"" + s2 + "\" = \"" + s3 + "\"");

  }
}

Result

Quiz