Method retainFrom

guava/src/com/google/common/base/CharMatcher.java:657–659

Returns a string containing all matching BMP characters of a character sequence, in order. For example: {@snippet : CharMatcher.is('a').retainFrom("bazaar") } ... returns {@code "aaa"}.

(CharSequence sequence)

   * ... returns {@code "aaa"}.
   */
  public String retainFrom(CharSequence sequence) {
    return negate().removeFrom(sequence);
  }

  /**
   * Returns a string copy of the input character sequence, with each matching BMP character