lx3_6.java

jbuilder2005

//lx3_7.java

import java.io.*;
public class  lx3_7{
    public static void main(String args[ ])
    {
        double PI=3.141592654D;	//定义常量  
        double r=0, area;
        String S="";
        System.out.println ( "圆的半径为：");
        try{
           BufferedReader in=new BufferedReader(new InputStreamReader(System.in));
            S=in.readLine();
            r= Double.parseDouble (S);
            
        } catch(Exception e){} 
        area = PI * r * r;
        System.out.println ("面积为："+area);
    }
}