java统计文件中字母出现的频率

import java.io.File;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
public class a
{
public static void main(String args[])
{
File f=new File("1.txt");
if(f.isFile())
{
try
{
BufferedReader b=new BufferedReader(new FileReader(f));
StringBuffer sb=new StringBuffer();
String t;
while((t=b.readLine())!=null)
{
sb.append(t+"/n");
}
String s=sb.toString();
s.toLowerCase();
char tj[]=s.toCharArray();
int count[]=new int[26];
for(int i=0; i<s.length(); i++)
{
int j=tj[i]-'a';
if(j>=0&&j<26)
{
count[j]++;
System.out.println(count[j]*1.0/(s.length()-1));
}
}
}
catch(IOException e)
{
e.printStackTrace();
}
}
}
}