Simple message bus for in process communication.

MessageBus.java

import java.util.List;
import java.util.Objects;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.function.Consumer;

public class MessageBus {

  private static final MessageBus DEFAULT = new MessageBus();

  private final List<Consumer<Object>> consumers = new CopyOnWriteArrayList<>();

  public MessageBus() {
    // public ctor
  }

  static MessageBus getDefault() {
    return DEFAULT;
  }

  public void addConsumer(Consumer<Object> consumer) {
    Objects.requireNonNull(consumer, "The consumer cannot be null.");
    consumers.add(consumer);
  }

  public void removeConsumer(Consumer<Object> consumer) {
    Objects.requireNonNull(consumer, "The consumer cannot be null.");
    consumers.remove(consumer);
  }

  public void publish(Object value) {
    consumers.forEach(l -> l.accept(value));
  }
}