code: public static String cleanWhitespace(String str) {
          int length = str.length();
  
          StringBuffer buf = new StringBuffer(length);
          for (int i=0; i<length; i++) {
              char c = str.charAt(i);
              if (Character.isWhitespace(c)) {
                  buf.append(' ');
              }
              else {
                  buf.append(c);
              }
          }
  
          return buf.toString();
      }
docs: Converts all whitespace characters in a String to space characters
  (\u0020).