java letter frequency string

i was hoping someone could tell me how i can make my code as it is accept a string that has to be inputted into the code before running it. So basically my code right now asks for words(string) to be written by the user when its running i need to go back to just having string = "" i think something like that i edited this a lot. i hope i've not been silly with my description of what i need any help would be appreciated thank you.

 import java.io.*;
 public class testjavafile04
 { 
   public static void main(String args[]) throws IOException  
    {while(true)

    { BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
    System.out.print("Enter Words: ");
    String s = br.readLine();

    int l=s.length(); 
    s=s.toLowerCase(); 
    char ch;

    System.out.println("Letter\tCount");


    int count=0;                  
    int[] charcount= new int[26]; 
    for(int i=0; i<26; i++)charcount[i] = 0; 
    for(char i='a'; i<='z'; i++)
    {
      for(int j=0; j<l; j++)
      {
        ch=s.charAt(j); 
        if(ch==i) 
        {
          count++;           
          charcount[i-97]++; 
        }
      }

    }

      for(char i='a'; i<='z'; i++)
      {
          System.out.println(i+"\t"+ (float)charcount[i-97]*100/count);

      }
      }

    }      

}