JAVA新手问题!会的帮下忙!谢谢啦

import java.io.*;

public class Test{
public static void main(String[] args)
{
String[] s = new String[20];
boolean bl=true;

try
{
while(bl)
{
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
System.out.print("请输入一个数：");
s[0]=br.readLine();
for (int r = 0; r < s[0].length(); r++)
{
if (!(s[0].charAt(r) >= 48 && s[0].charAt(r) <= 57))
{
System.out.println("\t\t\t您输入的不是纯数字!请重新输入.");
bl=true;
break;
}
else
{
int a = Integer.parseInt(s[0]);

for(int b=1;b<=a;b++)
{
System.out.print("第"+"["+b+"]:");
s[1]=br.readLine();
bl=false;
}
}
}
}
}catch(IOException e){}
}