title: Count Chars in a String Java
body: <p>Hi I have a problem in my code, I have to count the variables used in an expression and when two or more variables are same it should be counted as 1. For example, a+ab = the total number of variable used: 2. The problem is when I inputted a+a =total number of variable used: 2.
  Here's my code:</p>
  
  <pre><code>public void simplify(String strexp){
      int ex =strexp.length();
  
      for (int a=0;a&lt;=ex-1;a++){
          if(a==0)
          {
          if (Character.isLetter(strexp.charAt(a)))
          {
          b++;
         }
  
  
          }
          else{
          for(int c=0;c&lt;=a-1;c++){
                if (Character.isLetter(strexp.charAt(c))==Character.isLetter(strexp.charAt(a)))
                {
  
                  System.out.println("equal");
                  break;
                }
                else if (Character.isLetter(strexp.charAt(c))!=Character.isLetter(strexp.charAt(a)))
                {
               //if(c==a-1)
                //{
                 b++;
                 System.out.println("nomatch");
             //  }
                 }
          }
          }
          }
     JOptionPane.showMessageDialog(null, b);
      }
  </code></pre>