code: public static String removeWhitespace(String string) {
  
          if (string == null || string.length() == 0) {
              return string;
          } else {
              int codePoints = string.codePointCount(0, string.length());
              StringBuilder sb = new StringBuilder();
  
              for (int i = 0; i < codePoints; i++) {
                  int offset = string.offsetByCodePoints(0, i);
  
                  int nextCodePoint = string.codePointAt(offset);
                  if (!Character.isWhitespace(nextCodePoint)) {
                      sb.appendCodePoint(nextCodePoint);
                  }
              }
  
              if (string.length() == sb.length()) {
                  return string;
              } else {
                  return sb.toString();
              }
          }
      }
docs: Removes any whitespace from a String, correctly handling surrogate characters
  @param string String to process
  @return String with any whitespace removed