public class RemoveDuplicateI {
  // Try to convert the input to char[],
  // and do it in place.
  public String deDup(String input) {
    if (input == null) {
      return null;
    }
    char[] array = input.toCharArray();
    int end = 0;
    for (int i = 0; i < array.length; i++) {
      // repeated characters will be ignored except
      // for the first character in the sequence.
      if (i == 0 || array[i] != array[end - 1]) {
        array[end++] = array[i];
      }
    }
    return new String(array, 0, end);
  }
}