简单模拟了一下 node 的事件类

EventMain.java

public class EventMain {
	
	
	public static class Emitter {

		private ConcurrentMap<String, ConcurrentLinkedQueue<Listener>> mCallbacks = new ConcurrentHashMap<String, ConcurrentLinkedQueue<Listener>>();

		private ConcurrentHashMap<Listener, Listener> mOnceCallback = new ConcurrentHashMap<Emitter.Listener, Emitter.Listener>();

		public Emitter on(String event, Listener fn) {
			ConcurrentLinkedQueue<Listener> callbacks = this.mCallbacks.get(event);

			if (callbacks == null) {
				
				callbacks = new ConcurrentLinkedQueue<Emitter.Listener>();
				
				ConcurrentLinkedQueue<Listener> _callbacks = this.mCallbacks
						.putIfAbsent(event, callbacks);
				
				if (_callbacks != null) {
					callbacks = _callbacks;
				}
			}
			
			callbacks.add(fn);

			return this;
		}
		
		
		/**只用一次的时间
		 * @param event
		 * @param fn
		 * @return
		 */
		public Emitter once(final String event, final Listener fn){
			Listener on = new Listener() {
				
				@Override
				public void call(Object... args) {
					Emitter.this.off(event, this);
					fn.call(args);;
				}
			};
			
			this.mOnceCallback.put(fn, on);
			this.on(event, on);
			
			return this;
		}

		
		/**取消某个事件
		 * @param event
		 * @param fn
		 * @return
		 */
		public Emitter off(String event, Listener fn) {
			ConcurrentLinkedQueue<Listener> callbacks = this.mCallbacks.get(event);
			
			if(callbacks != null){
				// 优先取消 once 的事件
				Listener off = this.mOnceCallback.remove(fn);
				callbacks.remove(off != null ? off : fn);
			}
			
			return this;
		}
		
		public Emitter emit(String event, Object... args){
			ConcurrentLinkedQueue<Listener> callbacks = this.mCallbacks.get(event);
			
			if(callbacks != null){
				callbacks = new ConcurrentLinkedQueue<Emitter.Listener>(callbacks);
				for(Listener fn : callbacks){
					fn.call(args);
				}
			}
			
			return this;
		}
		
		public static interface Listener {

			public void call(Object... args);
		}

	}
	
	public static class TestEvent extends Emitter {
		
		
	}
	
	
	public static void main(String[] args) {
	
		TestEvent te = new TestEvent();
		
		te.on("fsck", new Listener() {
			
			@Override
			public void call(Object... args) {
				System.out.println(args[0]);
			}
		});
		
		
		te.emit("fsck", "disk");
	}
}