guava/src/com/google/common/escape/ArrayBasedCharEscaper.java
@Override
  protected final char[] escape(char c) {
    if (c < replacementsLength) {
      char[] chars = replacements[c];
      if (chars != null) {
        return chars;
      }
    }
    if (c >= safeMin && c <= safeMax) {
      return null;
    }
    return escapeUnsafe(c);
  }
@Override
  protected final char[] escape(char c) {
    if (c < replacementsLength) {
      char[] chars = replacements[c];
      if (chars != null) {
        return chars;
      }
    }
    if (c >= safeMin && c <= safeMax) {
      return null;
    }
    return escapeUnsafe(c);
  }
Escapes a single character using the replacement array and safe range values. If the given
character does not have an explicit replacement and lies outside the safe range then {@link
#escapeUnsafe} is called.