code: void writeString(String value) throws IOException {
          output.append('"');
          for (int i = 0; i < value.length(); i++) {
              char ch = value.charAt(i);
              if (ch < 128) {
                  String replace = REPLACE[ch];
                  if (replace != null) {
                      output.append(replace);
                  } else {
                      output.append(ch);
                  }
              } else if (ch == '\u2028') {
                  output.append("\\u2028");  // match other JSON writers
              } else if (ch == '\u2029') {
                  output.append("\\u2029");  // match other JSON writers
              } else {
                  output.append(ch);
              }
          }
          output.append('"');
      }
docs: Writes a JSON string.
  
  @param value  the value
  @throws IOException if an error occurs