int p = 0;
    while (p < maxPrefixLength && a.charAt(p) == b.charAt(p)) {
      p++;
    }
    if (validSurrogatePairAt(a, p - 1) || validSurrogatePairAt(b, p - 1)) {
      p--;
    }
    return a.subSequence(0, p).toString();
  }

  /**
   * Returns the longest string {@code suffix} such that {@code a.toString().endsWith(suffix) &&

            int codePoint = Character.codePointAt(input, i);
            if (codePoint == c) {
              // fall back to JDK getBytes instead of trying to handle invalid surrogates ourselves
              putBytes(input.subSequence(i, utf16Length).toString().getBytes(charset));
              return this;
            }
            i++;
            update(4, codePointToFourUtf8Bytes(codePoint));
          }
        }
        return this;

        break;
      }
    }
    for (last = len - 1; last > first; last--) {
      if (!matches(sequence.charAt(last))) {
        break;
      }
    }

    return sequence.subSequence(first, last + 1).toString();
  }

  /**
   * Returns a substring of the input character sequence that omits all matching BMP characters from
   * the beginning of the string. For example:
   *

                public int length() {
                    return name.length();
                }

                @Override
                public CharSequence subSequence(final int start, final int end) {
                    return name.subSequence(start, end);
                }

            };
        }

        /**
         * @return CharSequence
         */

        break;
      }
    }
    for (last = len - 1; last > first; last--) {
      if (!matches(sequence.charAt(last))) {
        break;
      }
    }

    return sequence.subSequence(first, last + 1).toString();
  }

  /**
   * Returns a substring of the input character sequence that omits all matching BMP characters from
   * the beginning of the string. For example:
   *

    assertEquals(Strings.repeat("ZZ", s.length()), matcher.replaceFrom(s, "ZZ"));
    assertEquals("", matcher.trimFrom(s));
    assertEquals(s.length(), matcher.countIn(s));
  }

  // Kotlin subSequence()/replace() always return new strings, violating expectations of this test
  @J2ktIncompatible
  public void testGeneral() {
    doTestGeneral(is('a'), 'a', 'b');
    doTestGeneral(isNot('a'), 'b', 'a');

    assertEquals(Strings.repeat("ZZ", s.length()), matcher.replaceFrom(s, "ZZ"));
    assertEquals("", matcher.trimFrom(s));
    assertEquals(s.length(), matcher.countIn(s));
  }

  // Kotlin subSequence()/replace() always return new strings, violating expectations of this test
  @J2ktIncompatible
  public void testGeneral() {
    doTestGeneral(is('a'), 'a', 'b');
    doTestGeneral(isNot('a'), 'b', 'a');

      char padChar = paddingChar.charValue();
      int l;
      for (l = chars.length() - 1; l >= 0; l--) {
        if (chars.charAt(l) != padChar) {
          break;
        }
      }
      return chars.subSequence(0, l + 1);
    }

    @Override
    public boolean canDecode(CharSequence chars) {
      checkNotNull(chars);
      chars = trimTrailingPadding(chars);