///
/// exception handling
///
main(List<String> args) {
  // try ..on, 一般用于处理已知错误
  try {
    int result = 12 ~/ 0;
    print("The result is $result");
  } on IntegerDivisionByZeroException {
    print('Cannot divide by Zero');
  }

  // try ..catch, 一般用于捕获未知错误
  try {
    int result = 12 ~/ 0;
    print("The result is $result");
  } catch (e) {
    print("The exception thrown is $e");
  }

  // STACK TRAC
  try {
    int result = 12 ~/ 0;
    print("The result is $result");
  } catch (e, s) {
    print("The exception thrown is $e");
    print("STACK TRACE \n $s");
  }

  // finally
  try {
    int result = 12 ~/ 0;
    print("The result is $result");
  } catch (e) {
    print("The exception thrown is $e");
  } finally {
    print("This is FINALLY Clause and is always executed.");
  }

  // try ..finally
  try {
    int result = 12 ~/ 1;
    print("The result is $result");
  } finally {
    print("This is FINALLY Clause and is always executed.");
  }

  // Custom Exception
  try {
    throwFunc();
  } catch (e) {
    print(e);
  }
}

class CustomException implements Exception {
  @override
  String toString() {
    return "This is Custom Exception.";
  }
}

throwFunc() {
  throw CustomException();
}