PrinterErrors.java

package main.java.kyu7;

/**
 * 7 kyu - Printer Errors
 *
 * https://www.codewars.com/kata/56541980fa08ab47a0000040
 *
 * Details:
 *
 * In a factory a printer prints labels for boxes. For one kind of boxes the printer has to use
 * colors which, for the sake of simplicity, are named with letters from a to m.
 *
 * The colors used by the printer are recorded in a control string. For example a "good" control
 * string would be aaabbbbhaijjjm meaning that the printer used three times color a, four times
 * color b, one time color h then one time color a...
 *
 * Sometimes there are problems: lack of colors, technical malfunction and a "bad" control string
 * is produced e.g. aaaxbbbbyyhwawiwjjjwwm with letters not from a to m.
 *
 * You have to write a function printer_error which given a string will output the error rate of
 * the printer as a string representing a rational whose numerator is the number of errors and the
 * denominator the length of the control string. Don't reduce this fraction to a simpler expression.
 *
 * The string has a length greater or equal to one and contains only letters from ato z.
 */

public class PrinterErrors {
    public static String printerError(String s) {
        int count = 0;

        for (int i = 0; i < s.length(); i++) {
            if ("nopqrstuvwxyz".indexOf(s.charAt(i)) >= 0) {
                count++;
            }
        }

        return String.format("%d/%d", count, s.length());
    }
}