1、可以抛出任何非null对象

throw Exception('Something bad happened.');

throw 'Waaaaaaah!';

//异常处理

try {

  breedMoreLlamas();

} on OutOfLlamasException {

  //处理特定异常

  buyMoreLlamas();

} on Exception catch (e) {

  // 其他任何异常

  print('Unknown exception: $e');

} catch (e) {

  // 其他类型

  print('Something really unknown: $e');

}

2、处理后可以重新抛出

try {

  breedMoreLlamas();

} catch (e) {

  print('I was just trying to breed llamas!.');

  rethrow;

}

3、finally 肯定执行代码块

try {

  breedMoreLlamas();

} catch (e) {

  // ... handle exception ...

} finally {

  // Always clean up, even if an exception is thrown.

  cleanLlamaStalls();

}