class SuperEx {
String r;
String s;
public SuperEx(String a, String b) {
r = a;
s = b;
}
public void aMethod(){
System.out.println("r:"+r);
}
}

class SubEx extends SuperEx {
public SubEx(String a, String b){
super(a, b);
}
public static void main(String[] args){
SuperEx a = new SuperEx("Hi", "Tom");
SuperEx b = new SubEx("Hi", "Bart");
a.aMethod();
b.aMethod();
}
public void aMethod(){
System.out.println("r:"+r+"s:"+s);
}
}
5，sub 求给解流程

a.aMethod();的结果为"Hi:"Hi,    new SubEx("Hi","Bart")  走的是父类SupeEx的构造方法，b.aMethod();多态引用指向子类对象，执行子类的aMethod();方法。     最后结果为"Hi:"Hi      "Hi:"Hi"Bart:"Bart