我是新手，刚学的．不知道这个程序错在哪了．．请高手指点！！谢谢．不胜感激～





class yuan
{
int b;
final double PI=3.1415926;

int mianji()
{
return (int)(PI*((double)b)*((double)b);
}
int zhouchang()
{
return (int)(2*((double)b)*PI);
}
public static void main( String[] args)
{

yuan y1=new yuan();
yuan y2=new yuan();
y1.b=2;
System.out.println("mianji of yuan="+y1.mianji());
System.out.println("zhouchang of yuan="+y1.zhouchang());
y2.b=4;
System.out.println("mianji of yuan="+y2.mianji());
System.out.println("zhouchang of yuan="+y2.zhouchang());
}
}

[此贴子已经被作者于2007-9-22 2:52:29编辑过]

class yuan
{
int b;
final double PI=3.1415926;

int mianji()
{
return (int)(PI*((double)b)*((double)b));//这少了一个括号，
}
int zhouchang()
{
return (int)(2*((double)b)*PI);
}
public static void main( String[] args)
{

yuan y1=new yuan();
yuan y2=new yuan();
y1.b=2;
System.out.println("mianji of yuan="+y1.mianji());
System.out.println("zhouchang of yuan="+y1.zhouchang());
y2.b=4;
System.out.println("mianji of yuan="+y2.mianji());
System.out.println("zhouchang of yuan="+y2.zhouchang());
}
}

谢谢楼上，我改了后，怎么运行它提示这个：
Exception in thread "main" java.lang.NoSuchMethodError: main
哪的错？

你运行java命令的时候，类名可能写错了！！
仔细检查下

没有啊．不可能错的．谢谢你咯．在帮我找找问题～

应试是环境变量设置问题?在重设一下!

把你运行的代码贴出来，
呵呵，这样太抽象了！！

我运行的时候该一下类名yuan要大写（Yuan）, 在第八行加了一个“）”就 OK了。运行的结果为：
mianji of yuan=12
zhouchang of yuan=12
mianji of yuan=50
zhouchang of yuan=25
不知正不正确啊？

大小没关系吧 编译时一样就可以了啊

import java.io.*;
class yuan
{
int b;
final double PI=3.1415926;

int mianji()
{
return (int)(PI*((double)b)*((double)b));
}
int zhouchang()
{
return (int)(2*((double)b)*PI);
}

public static void main( String[] args)throws IOException
{

yuan y1=new yuan();
yuan y2=new yuan();
int c;
System.out.println("shuru:");
c=System.in.read();
y1.b=c;
System.out.println("mianji of yuan="+y1.mianji());
System.out.println("zhouchang of yuan="+y1.zhouchang());
y2.b=4;
System.out.println("mianji of yuan="+y2.mianji());
System.out.println("zhouchang of yuan="+y2.zhouchang());
}
}


为什么我输入4后得到的结果是：
mianji of yuan=8494
zhouchang of yuan=326
mianji of yuan=50
zhouchang of yuan=25