Moon.java

package com.insightfullogic.java8.examples.chapter8.observer;

import java.util.ArrayList;
import java.util.List;

// BEGIN Moon
public class Moon {

    private final List<LandingObserver> observers = new ArrayList<>();

    public void land(String name) {
        for (LandingObserver observer : observers) {
            observer.observeLanding(name);
        }
    }

    public void startSpying(LandingObserver observer) {
        observers.add(observer);
    }
// END Moon

    public static void main(String[] args) {
        classBasedExample();
        lambdaBasedExample();
    }

    private static void classBasedExample() {
// BEGIN classBasedExample
Moon moon = new Moon();
moon.startSpying(new Nasa());
moon.startSpying(new Aliens());

moon.land("An asteroid");
moon.land("Apollo 11");
// END classBasedExample
    }

    private static void lambdaBasedExample() {
// BEGIN lambdaBasedExample
Moon moon = new Moon();

moon.startSpying(name -> {
    if (name.contains("Apollo"))
        System.out.println("We made it!");
});

moon.startSpying(name -> {
    if (name.contains("Apollo"))
        System.out.println("They're distracted, lets invade earth!");
});

moon.land("An asteroid");
moon.land("Apollo 11");
// END lambdaBasedExample
    }

}