}

          // Inefficient implementation that defines all letters as escapable.
          @Override
          protected int nextEscapeIndex(CharSequence csq, int index, int end) {
            while (index < end && !Character.isLetter(csq.charAt(index))) {
              index++;
            }
            return index;
          }
        };

            }
        }
        return input;
    }

    public boolean hasUAMathcer() {
        return StringUtil.isNotBlank(getUserAgent());
    }

    public Matcher getUAMatcher(final CharSequence input) {
        if (!hasUAMathcer()) {
            return null;
        }

        if (userAgentPattern == null) {
            userAgentPattern = Pattern.compile(getUserAgent());
        }

   * @since 3.0
   */
  @GwtIncompatible // Only used by other GWT-incompatible code.
  public static Predicate<CharSequence> containsPattern(String pattern) {
    return new ContainsPatternFromStringPredicate(pattern);
  }

  /**
   * Returns a predicate that evaluates to {@code true} if the {@code CharSequence} being tested
   * contains any match for the given regular expression pattern. The test used is equivalent to

    return new Appendable() {

      @Override
      public Appendable append(CharSequence csq) throws IOException {
        a.append(csq);
        return this;
      }

      @Override
      public Appendable append(CharSequence csq, int start, int end) throws IOException {
        a.append(csq, start, end);
        return this;
      }

      @Override

    return new Appendable() {

      @Override
      public Appendable append(CharSequence csq) throws IOException {
        a.append(csq);
        return this;
      }

      @Override
      public Appendable append(CharSequence csq, int start, int end) throws IOException {
        a.append(csq, start, end);
        return this;
      }

      @Override

    assertEquals(-1, Iterables.indexOf(list, equalTo("jack")));
  }

  private static final Predicate<CharSequence> STARTSWITH_A =
      new Predicate<CharSequence>() {
        @Override
        public boolean apply(CharSequence input) {
          return (input.length() > 0) && (input.charAt(0) == 'a');
        }
      };

  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 void testRepeat_null() {
    assertThrows(NullPointerException.class, () -> Strings.repeat(null, 5));
  }

  @SuppressWarnings("UnnecessaryStringBuilder") // We want to test a non-String CharSequence
  public void testCommonPrefix() {
    assertEquals("", Strings.commonPrefix("", ""));
    assertEquals("", Strings.commonPrefix("abc", ""));
    assertEquals("", Strings.commonPrefix("", "abc"));

    }

    private static boolean isEmpty(Object value) {
      // Put types estimated to be the most frequent first.
      if (value instanceof CharSequence) {
        return ((CharSequence) value).length() == 0;
      } else if (value instanceof Collection) {
        return ((Collection<?>) value).isEmpty();
      } else if (value instanceof Map) {

    }
    if (cp >= safeMin && cp <= safeMax) {
      return null;
    }
    return escapeUnsafe(cp);
  }

  /* Overridden for performance. */
  @Override
  protected final int nextEscapeIndex(CharSequence csq, int index, int end) {
    while (index < end) {
      char c = csq.charAt(index);
      if ((c < replacementsLength && replacements[c] != null)
          || c > safeMaxChar
          || c < safeMinChar) {