如何在Java/Kotlin中重写另一个类实例的方法？

class ParentClass {
    public void printMessage() {
        System.out.println("Hello, World!");
    }
}

class ChildClass extends ParentClass {
    @Override
    public void printMessage() {
        System.out.println("Hello, Cloud Computing!");
    }
}

public class Main {
    public static void main(String[] args) {
        ParentClass parent = new ParentClass();
        ChildClass child = new ChildClass();

        parent.printMessage();  // 输出：Hello, World!
        child.printMessage();   // 输出：Hello, Cloud Computing!
    }
}

open class ParentClass {
    open fun printMessage() {
        println("Hello, World!")
    }
}

class ChildClass : ParentClass() {
    override fun printMessage() {
        println("Hello, Cloud Computing!")
    }
}

fun main() {
    val parent = ParentClass()
    val child = ChildClass()

    parent.printMessage()  // 输出：Hello, World!
    child.printMessage()   // 输出：Hello, Cloud Computing!
}