import java.io.*;
import java.util.Scanner;
class jisuan
{
int c;
class fourcount
{
double a,b;
double sum,del,che,chu;
double Sum(double a,double b)
{
sum=a+b;
return sum;
}
double del(double a,double b)
{
del=a-b;
return del;
}
double che(double a,double b)
{
che=a*b;
return che;
}
double chu(double a,double b)
{
chu=a/b;
return chu;
}
}
class jszl extends jisuan
{
//这里它说sum没有定义,不是继承了jisuan里面的吗
double Sum(double a,double b)
{
sum=(a+b)*2;
return sum;
}
}
jszl b=new jszl();
System.out(b.Sum(2.0, 3.0));//怎么不能调用Sum函数
}