JAVA huffman树统计字符出现的次数（权值）

import java.util.Scanner;

public class Weigh_
{
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);

System.out.println("Enter a string:");

String s = input.nextLine();

int[] counts = countletters(s);

for(int i = 0;i < counts.length; i++)
{
if(counts[i]!=0)
System.out.println((char)(' ' + i) + " appears " + counts[i] + ((counts[i]==1)? " time" : " times"));
}
}

public static int[] countletters(String s)
{
int[] counts = new int[127];

for(int i = 0; i < s.length(); i++)
{
if(Character.isLetter(s.charAt(i)))
counts[s.charAt(i) - ' ']++;
}
return counts;
}

这是我写的代码，可是只能输入小写字母，而且没法统计符号出现的次数，新手入门，请大神指教。。。要怎么改？？多谢。。

http://bbs.csdn.net/topics/391962897