wkdalsgh192

// Creata a hash map class and put values into the map
Map<String, String> map = new HashMap<>();
map.put("1", "A");
map.put("2", "B");
map.put("3", "C");


// Create a class that only contains a collection.
public class GameRanking {

wkdalsgh192

// 2. Pass a function as a parameter
function sayHello() {
   return "Hello, ";
}
function greeting(helloMessage, name) {
  console.log(helloMessage() + name);
}

greeting(sayHello, "JavaScript!");

wkdalsgh192

// 1. Assign a function to a variable
const sayHello = function() {
   console.log("Hello");
  return "Hello, ";
}
// Invoke it using the variable
sayHello();

wkdalsgh192

// Using a callback method
CompletableFuture<String> future4 = CompletableFuture.supplyAsync(() -> {
    System.out.println("Hello "+ Thread.currentThread().getName());
    return "Hello";
}).thenApply((s) -> { // thenApply, thenAccept or thenRun can also be used here
    System.out.println(Thread.currentThread().getName());
    return s.toUpperCase(Locale.ROOT);
});

System.out.println(future4.get());

wkdalsgh192

// when there is no return value
CompletableFuture<Void> future2 = CompletableFuture.runAsync(() -> {
    System.out.println("Hello "+ Thread.currentThread().getName());
});
future2.get(); // get() should be called to execute the thread


// when there is a return value
CompletableFuture<String> future3 = CompletableFuture.supplyAsync(() -> {
    System.out.println("HEllo " + Thread.currentThread().getName());

wkdalsgh192

ExecutorService executorService = Executors.newSingleThreadExecutor();

Callable<String> hello = () -> {
            Thread.sleep(2000L);
            return "Hello";
        };

Callable<String> java = () -> {
            Thread.sleep(3000L);
            return "Java";

wkdalsgh192

// new single thread created and managed by executor service
ExecutorService executorService = Executors.newSingleThreadExecutor(); 

Callable<String> hello = () -> {
    Thread.sleep(2000L);
    return "Hello";
};

Future<String> submit = executorService.submit(hello); // callable object executed and falls asleep for 2 sec
System.out.println(submit.isDone()); // main thread keep running - 1

wkdalsgh192

Thread newThread = new Thread(() -> {
            System.out.println("Thread : "+ Thread.currentThread().getName());
            try {
                Thread.sleep(2000L);
            } catch (InterruptedException e) {
                System.out.println("Exit!");
                return;
            }
        });

wkdalsgh192

Thread newThread = new Thread(() -> {
           while (true) {
               System.out.println("Thread : "+ Thread.currentThread().getName());
               try {
                   Thread.sleep(2000L);
               } catch (InterruptedException e) {
                   System.out.println("Exit!");
                   return;
               }
           }

wkdalsgh192

Thread thread = new Thread(() -> {

            try {
                Thread.sleep(1000L);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("Thread : "+ Thread.currentThread().getName());
        });