* {@code b} have no common prefix, returns the empty string.
   *
   * @since 11.0
   */
  public static String commonPrefix(CharSequence a, CharSequence b) {
    checkNotNull(a);
    checkNotNull(b);

    int maxPrefixLength = Math.min(a.length(), b.length());
    int p = 0;
    while (p < maxPrefixLength && a.charAt(p) == b.charAt(p)) {
      p++;

  private static final Appendable NASTY_APPENDABLE =
      new Appendable() {
        @Override
        public Appendable append(@Nullable CharSequence csq) throws IOException {
          throw new IOException();
        }

        @Override
        public Appendable append(@Nullable CharSequence csq, int start, int end)
            throws IOException {
          throw new IOException();
        }

        @Override

    public <T> Iterable<? super String> wildcardsMatchByLowerBound(
        List<? super CharSequence> list) {
      return isSubtype(list);
    }

    @TestSubtype(suppressGetSupertype = true, suppressGetSubtype = true)
    public <T> Iterable<? super CharSequence> wildCardsDoNotMatchByLowerBound(
        List<? super String> list) {
      return notSubtype(list);
    }

   * the {@code charSequence} is mutated while it is being read, so don't do that.
   *
   * @since 15.0 (since 14.0 as {@code CharStreams.asCharSource(String)})
   */
  public static CharSource wrap(CharSequence charSequence) {
    return charSequence instanceof String
        ? new StringCharSource((String) charSequence)
        : new CharSequenceCharSource(charSequence);
  }

  /**

  public void testContainsPattern_apply() {
    Predicate<CharSequence> isFoobar = Predicates.containsPattern("^Fo.*o.*bar$");
    assertTrue(isFoobar.apply("Foxyzoabcbar"));
    assertFalse(isFoobar.apply("Foobarx"));
  }

  @GwtIncompatible // Predicates.containsPattern
  public void testContains_apply() {
    Predicate<CharSequence> isFoobar = Predicates.contains(Pattern.compile("^Fo.*o.*bar$"));

     * tolerance is implemented differently: Its implementation avoids calling this toString(Object)
     * method in the first place.)
     */
    requireNonNull(part);
    return (part instanceof CharSequence) ? (CharSequence) part : part.toString();
  }

  private static Iterable<@Nullable Object> iterable(
      @CheckForNull Object first, @CheckForNull Object second, @Nullable Object[] rest) {
    checkNotNull(rest);

   * surprising behavior of {@code toUpperCase()} and {@code toLowerCase()}.
   *
   * @since 16.0
   */
  public static boolean equalsIgnoreCase(CharSequence s1, CharSequence s2) {
    // Calling length() is the null pointer check (so do it before we can exit early).
    int length = s1.length();
    if (s1 == s2) {
      return true;
    }
    if (length != s2.length()) {

   * {@link #splitToList(CharSequence)}. Java 8+ users may prefer {@link #splitToStream} instead.
   *
   * @param sequence the sequence of characters to split
   * @return an iteration over the segments split from the parameter
   */
  public Iterable<String> split(final CharSequence sequence) {
    checkNotNull(sequence);

    return new Iterable<String>() {

  abstract int maxDecodedSize(int chars);

  abstract int decodeTo(byte[] target, CharSequence chars) throws DecodingException;

  CharSequence trimTrailingPadding(CharSequence chars) {
    return checkNotNull(chars);
  }

  // Modified encoding generators

  /**

   * Iterator}, which may be lazily evaluated. If you want an eagerly computed {@link List}, use
   * {@link #splitToList(CharSequence)}.
   *
   * @param sequence the sequence of characters to split
   * @return an iteration over the segments split from the parameter
   */
  public Iterable<String> split(final CharSequence sequence) {
    checkNotNull(sequence);

    return new Iterable<String>() {
      @Override