code: public static void appendCompactedString(final StringBuilder destination, final String source) {
          boolean previousIsWhiteSpace = false;
          int length = source.length();
  
          for (int i = 0; i < length; i++) {
              char ch = source.charAt(i);
              if (isWhiteSpace(ch)) {
                  if (previousIsWhiteSpace) {
                      continue;
                  }
                  destination.append(CHAR_SPACE);
                  previousIsWhiteSpace = true;
              } else {
                  destination.append(ch);
                  previousIsWhiteSpace = false;
              }
          }
      }
docs: This method appends a string to a string builder and collapses contiguous
  white space is a single space.
  
  This is equivalent to:
  destination.append(source.replaceAll("\\s+", " "))
  but does not create a Pattern object that needs to compile the match
  string; it also prevents us from having to make a Matcher object as well.