将内部类写为static的可以实现和外部类相同的调用方式

public class StaticDispatch {

	abstract class Human {
	}

	class Man extends Human {
	}

	class Woman extends Human {
	}

	public void sayHello(Human guy) {
		System.out.println("hello,guy!");
	}

	public void sayHello(Man guy) {
		System.out.println("hello,gentleman!");
	}

	public void sayHello(Woman guy) {
		System.out.println("hello,lady!");
	}

	public static void main(String[] args) {
		StaticDispatch staticDispatch = new StaticDispatch();
		Human man = staticDispatch.new Man();
		Human woman = staticDispatch.new Woman();
		StaticDispatch sr = new StaticDispatch();
		sr.sayHello(man);
		sr.sayHello(woman);
	}
}