As a good programmer, you test your app in all possible conditions. Dart defines a number of errors for those things that you should remedy in your code, such as
CastError when a cast fails, or
NoSuchMethodError when the class of the object on which the method is called does not have this method, and neither does any of its parent classes. All these are subclasses of the
Error class, and you should code so that they do not occur. However, when something unexpected occurs while running the app and the code cannot cope with it,
Unhandled Exception occurs. Especially, the input values that are read in from the keyboard, a file, or a network connection are dangerous. Suppose the input is such a value ...