091108 t throw exception

For writeProgramA small problem for people with high speed is as follows:
(Original method)
Void method (Object Arg ){
String name = Arg. tostring ();
}

(New method)
Void method (Object Arg ){
If (ARG = NULL) throw new argumentnullexception ();
String name = Arg. tostring ();
}

Here we should execute the display judgment on the parameter Arg and throw an exception.
Although the original method will throw an exception when Arg is null, there are two failures:
1. The thrown exception is not the specified argumentnullexception, but the default nullreferenceexception.
2. (important) if the exception is self-controlled, it should be thrown explicitly! The reason is Readability: when someone else reads this program, they will not think that the author has not considered this problem.