babjo

public class ClassA {
	private Collaborator collaborator1;
	private Collaborator collaborator2;
	
	public void methodA() { // changed
            ...
	}
		
	public void methodB() { // affected as well
            ...

babjo

public class SendKakaoCommand implements Command { // new
        ...
	public void execute() {
		...
	}
}

babjo

public class Handler {
	...
	public void handle(Command command) {
		command.execute();
	}
}
interface Command {
	public void execute();
}
public class SendEmailCommand implements Command {

babjo

public class Handler {
    ...
    public void handle(Command command) {
        switch (command.getType()) {
            case SEND_EMAIL:
                String subject = command.getSubject();
                String body = renderBody(command.getType(), command.getBodyParams());
                emailSender.send(new Email(subject, body));
                break;
            case SEND_KAKAO: // new

babjo

public class Handler {
    ...
    public void handle(Command command) {
        switch (command.getType()) {
            case SEND_EMAIL:
                String subject = command.getSubject();
                String body = renderBody(command.getType(), command.getBodyParams());
                emailSender.send(new Email(subject, body));
                break;
            default:

babjo

curl https://download.java.net/java/ga/jdk11/openjdk-11_osx-x64_bin.tar.gz \
 | tar -xz \
 && sudo mv jdk-11.jdk /Library/Java/JavaVirtualMachines

babjo

// use a lambda expression to create the initial listener
// which does nothing
HyperlinkListener listener = event -> {};

// these decorators first do their own thing and then call the
// decorated listener (the one handed over during construction);
// in the end, the last added decorator will act first
listener = new ExternalApplicationOpeningHyperlinkListenerDecorator(listener);
listener = new BrowserOpeningHyperlinkListenerDecorator(listener);
listener = new ServiceRequestHandlingHyperlinkListenerDecorator(listener);

babjo

CompletableFuture<String> completableFuture  
  = CompletableFuture.supplyAsync(() -> "Hello");
 
CompletableFuture<String> future = completableFuture
  .thenApplyAsync(s -> s + " World");
 
assertEquals("Hello World", future.get());

babjo

CompletableFuture<String> completableFuture = new CompletableFuture<>();
 
// ...
 
completableFuture.completeExceptionally(
  new RuntimeException("Calculation failed!"));
 
// ...
 
completableFuture.get(); // ExecutionException

babjo

String name = null;
 
// ...
 
CompletableFuture<String> completableFuture  
  =  CompletableFuture.supplyAsync(() -> {
      if (name == null) {
          throw new RuntimeException("Computation error!");
      }
      return "Hello, " + name;