Classes that use asynchronous method calls

AnswerAsyncClasses.java

class MyService {

    private final Client client;

    public MyService(Client client) {
        this.client = client;
    }

    StringBuilder getData() {
        StringBuilder data = new StringBuilder();
        client.processData(() -> {
            try {
                Thread.sleep(3000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            data.append("Here's your data!");
        });
        return data;
    }
}

@Component
class Client {

    public void processData(Runnable runnable) {
        runnable.run();
    }
}