Nested or sequential try-catch blocks?

simple-atoi.java

/**
 * Using nested try-catch blocks.
 *
 * @param str a string representing an integer
 * @return smallest integer type or null
 */
Number atoi_NestedTryCatch(String str) {
  try {
    return Integer.valueOf(str);
  } catch (NumberFormatException ignore1) {
    try {
      return Long.valueOf(str);
    } catch (NumberFormatException ignore2) {
      try {
        return new BigInteger(str);
      } catch (NumberFormatException ignore3) {
        return null;
      }
    }
  }
}

/**
 * Using sequential try-catch blocks.
 *
 * @param str a string representing an integer
 * @return smallest integer type or null
 */
Number atoi_SequentialTryCatch(String str) {
  try {
    return Integer.valueOf(str);
  } catch (NumberFormatException ignore1) {}
  try {
    return Long.valueOf(str);
  } catch (NumberFormatException ignore2) {}   
  try {
    return new BigInteger(str);
  } catch (NumberFormatException ignore3) {}
  return null;
}