为什么在父类方法中加上final, myeclipse在运行时报错“could not find main class.program will exit."

public class shuxi {

public static void main(String args[]){
A a=new B();
a.Ab();

}
}
class A{
public final void Ab(){
System.out.println("g");
}
}
class B extends A{
public void Ab(){
System.out.println("b");
}
}