title: Improve code check frequency of character in a string
body: <p>I wrote this code today to check frequency of each character in string. It runs quite slowly. How can I improve this code ?</p>
  
  <pre><code>import java.util.*;
  public class checkFreq {
  
      public static void main(String[] args) {
  
          Scanner s = new Scanner(System.in);
          // Input
          System.out.print("Enter a string: ");
          String input = s.nextLine();
          long t1 = System.currentTimeMillis();
          // Convert input to UpperCase
          String tmp = input.toUpperCase();
  
          // String to compare 
          String alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
          int aleng = alphabet.length();
  
          for (int l = 0; l &lt; aleng; l++) {
              //Run 26 times
              int count = 0;
              int i = 0;
              String tmp2;
              while (i &lt; tmp.length() - 1) {
                  tmp2 = tmp.substring(i, i + 1);
                  int exist = tmp2.indexOf(alphabet.charAt(l));
                  if (exist != -1) {
                      count++;
                  }
                  i++;
              }//End while
  
              if (count != 0) {
                  System.out.print(alphabet.charAt(l) + "(" + count + ") ");
              }//End if
          }// End for
          System.out.println();
  
          long t2 = System.currentTimeMillis();
          // Count time of process
          System.out.println("Time : " + (t2 - t1) + "ms");
      }
  }
  </code></pre>