driver-core/src/main/com/mongodb/internal/authentication/SaslPrep.java
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';
    }
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';
    }
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>.