How to detect control character (ex. 0x0A (line feed)) with java?

Question

I need to count the number of control characters from a text document.

Answer 1

Loop through your input char by char and compare the character's ordinal number with the control characters defined in ASCII standard. If you have a match, increase your counter.

---

Edit:

  String input = "325\nfefe\rw2";

  int normalCount = 0;
  int controlCount = 0;

  for (int i = 0; i < input.length(); ++i) {

     int characterCode = (int)input.charAt(i);

     if (characterCode == 10 || characterCode == 13) { // Match \n and \r
        ++controlCount;
     }
     else {
        ++normalCount;
     }
  }

  System.out.println("The input contains:");
  System.out.println("\t" + normalCount + " printable characters");
  System.out.println("\t" + controlCount + " control characters");

Will give you this output:

The input contains:
    9 printable characters
    2 control characters

Answer 2

Maybe you can find the isISOControl method from the Character class useful. It returns true is the character is a control character.

Supposing temp is a String and counter is an int where you want to have the total of control characters in the string, someting like this might do the trick:

   for (int i=0,counter=0;i<temp.length();i++) {
        if (!Character.isISOControl(temp.charAt(i))) {
            counter++;
        }
    }