code: private static boolean mappedToNothing(final char ch) {
          return ch == '\u00AD'
                  || ch == '\u034F'
                  || ch == '\u1806'
                  || ch == '\u180B'
                  || ch == '\u180C'
                  || ch == '\u180D'
                  || ch == '\u200B'
                  || ch == '\u200C'
                  || ch == '\u200D'
                  || ch == '\u2060'
                  || '\uFE00' <= ch && ch <= '\uFE0F'
                  || ch == '\uFEFF';
      }
docs: Return true if the given {@code ch} is a "commonly mapped to nothing" character as defined by
  <a href="https://tools.ietf.org/html/rfc3454#appendix-B.1">RFC 3454,
  Appendix B.1</a>.