重载-动态方法调度

时间：2010-10-15 来源：add358

阐述动态方法调度的例子：
// Dynamic Method Dispatch
class A {
   void callme() {
     System.out.println("Inside A's callme method");
}
}

class B extends A {
// override callme()
void callme() {
    System.out.println("Inside B's callme method");
}
}

class C extends A {
// override callme()
void callme() {
    System.out.println("Inside C's callme method");
}
}

class Dispatch {
public static void main(String args[]) {
    A a = new A(); // object of type A
    B b = new B(); // object of type B
    C c = new C(); // object of type C
    A r; // obtain a reference of type A

    r = a; // r refers to an A object
    r.callme(); // calls A's version of callme

    r = b; // r refers to a B object
    r.callme(); // calls B's version of callme
    r = c; // r refers to a C object
    r.callme(); // calls C's version of callme
}
}
该程序的输出如下：
Inside A’s callme method
Inside B’s callme method
Inside C’s callme method ！！被引用对象的类型（而不是引用变量的类型）决定执行哪个版本的重载方法。