[单例模式](%E5%8D%95%E4%BE%8B%E6%A8%A1%E5%BC%8F.md) [工厂模式](%E5%B7%A5%E5%8E%82%E6%A8%A1%E5%BC%8F.md) [观察者模式](%E8%A7%82%E5%AF%9F%E8%80%85%E6%A8%A1%E5%BC%8F.md) [责任链模式](%E8%B4%A3%E4%BB%BB%E9%93%BE%E6%A8%A1%E5%BC%8F.md)