Exception in thread "main" java.lang.NullPointerException at ysuan.main(ysuan.java:70)

import java.io.*;
class yunsuan{
int num1,num2,num3,Number;
float result;
char fuhao1,fuhao2;
yunsuan(int n1,int n2 ,int n3,char fh1,char fh2)
{
num1=n1;num2=n2;num3=n3;fuhao1=fh1;fuhao2=fh2;Number=3;}
yunsuan(int n1,int n2,char fh)
{num1=n1;num2=n2;fuhao1=fh;Number=2;}
public void jisuan()
{if(Number==2)
switch(fuhao1){
case '+': result=num1+num2;break;
case '-': result=num1-num2;break;
case '*': result=num1*num2;break;
case '/': result=num1/num2;break;
}
else if(Number==3)
{if(fuhao1=='+')
switch(fuhao2)
{case '+': result=num1+num2+num3;break;
case '-': result=num1+num2-num3;break;
case '*': result=num1+num2*num3;break;
case '/': result=num1+num2/num3;break;
}
else if(fuhao1=='-')
switch(fuhao2)
{c

Exception EOleSysError in module 英语作文，主题：in th park Realistic novel in the 18th century on June 5th和in June Christmas in the 13th Month nothing in thé world 是什么意思？ Report ranks China 6th in overall strength 怎么翻译？ 谁能告诉我feminism in 17th century 在英国 The film was released on 11th July in China Fashions in America before the 19th century_____those of Egland.