java - 使用反射在没有实例的情况下调用父类(super class)方法

Question

请考虑以下演示继承和反射的代码:

    /*Parent class*/

    package basics;

    public class Vehicle {

        private void parentPrivateMethod() {
            System.out.println("This is the child private method");
        }

        public void print() {
            System.out.println("This is a Vehicle method");
        }

        public void overrideThisMethod() {
            System.out.println("Parent method");
        }

    }


    /*Child class*/

    package basics;

    public class Car extends Vehicle {

        private void childPrivateMethod() {
            System.out.println("This is the child private method");
        }

        public String returnCarName() {
            return "Manza";
        }

        @Override
        public void overrideThisMethod() {
            //super.overrideThisMethod();/*NOTE THIS*/
            System.out.println("Child method");
        }

    }


    /*Tester class*/
    package basics;

    import java.lang.reflect.InvocationTargetException;
    import java.lang.reflect.Method;

    public class NewTester {

        /**
         * @param args
         * @throws NoSuchMethodException
         * @throws SecurityException
         * @throws InvocationTargetException
         * @throws IllegalAccessException
         * @throws IllegalArgumentException
         * @throws InstantiationException
         */
        public static void main(String[] args) throws SecurityException,
                NoSuchMethodException, IllegalArgumentException,
                IllegalAccessException, InvocationTargetException, InstantiationException {
            // TODO Auto-generated method stub

            Car carInstance = new Car();

            /* Normal method invocation */
            carInstance.overrideThisMethod();

            /* Reflection method invocation */
            Method whichMethod = Car.class.getSuperclass().getMethod(
                    "overrideThisMethod", null);
            whichMethod.invoke(carInstance, null);

            /* Work-around to call the superclass method */
            Method superClassMethod = Car.class.getSuperclass().getMethod(
                    "overrideThisMethod", null);
            superClassMethod.invoke(Car.class.getSuperclass().newInstance(), null);
        }

    }

输出(带有注释的“NOTE THIS”部分)是:

        Child method
        Child method
        Parent method

如果“注意这个”部分未被注释，父类(super class)方法将被调用，给出输出:

        Parent method
        Child method
        Parent method
        Child method
        Parent method

创建 Car 的实例时，首先运行 Vehicle 的构造函数。因此，我相信，也创建了一个 Vehicle 实例，Car 实例通过“super”持有其引用。

问题:如何在不使用/* 变通方法调用父类(super class)方法 */的情况下调用父类(super class)版本的“overrideThisMethod”？

我是否在这里忽略了什么/在这里做出了错误的假设？

Answer 1

When an instance of Car is created, the constructor of Vehicle runs first. Hence, I believe, that an instance of Vehicle is created,too, whose reference the Car instance holds via 'super'.

这不太正确；只创建一个对象。 Vehicle 的构造函数运行是因为它是 Vehicle 和 Car 的实例。没有单独的 Vehicle 对象，super 不是对象引用而是关键字。例如，您不能将 super 作为参数传递给方法。

super 关键字允许您告诉编译器您要从父类(super class)调用方法而不检查该方法是否在子类中被覆盖。为此，编译器使用 invokespecial JVM 指令生成方法调用。通常编译器会发出一条 invokevirtual 指令。