Java 超类引用子类对象的示例代码

动态方法分配 dynamic method dispatch
一个被重写的方法的调用会在运行时解析，而不是编译时解析
Java 会根据在调用发生时引用的对象的类型来判断所要执行的方法

public class DynamicMethodDispatch {
    void callSubClassMethod(subDynamicMethodDispatch d) {
        System.out.println("Call from SuperClass");
        d.subClassMethod();
        System.out.println("END CALL");
    }
    
    public static void main(String[] args) {
        DynamicMethodDispatch dispatch = new DynamicMethodDispatch();
        dispatch.callSubClassMethod(new subDynamicMethodDispatch());
        
        dispatch = new subDynamicMethodDispatch();
        dispatch.callSubClassMethod(dispatch);
    }
}

class subDynamicMethodDispatch extends DynamicMethodDispatch {
    void subClassMethod() {
        System.out.println("Method from subclass.");
    }
}