JCH
Java Community | Help. Code. Learn.•3d ago
sadstephen

Why does creating a subclass of some Exception, throws this error?

Custom exceptions are supposed to be caught if occurs, not intentionally thrown. 
jshell> class WrongInputException extends Exception {
   ...>     public String toString() {
   ...>        return "ERROR!!";
   ...>    }
   ...> }

jshell> try {
   ...>     ;
   ...> }
   ...> catch (ArithmeticException a) {
   ...>     ;
   ...> }            // <-------   compiles fine here

jshell> try {
   ...>     ;    // if I use throw new WrongInputException() it would have compiled perfectly
   ...> }
   ...> catch (WrongInputException a) {
   ...>     ;
   ...> }
|  Error:
|  exception WrongInputException is never thrown in body of corresponding try statement
|  catch (WrongInputException a) {
|  ^------------------------------...
jshell> class WrongInputException extends Exception {
   ...>     public String toString() {
   ...>        return "ERROR!!";
   ...>    }
   ...> }

jshell> try {
   ...>     ;
   ...> }
   ...> catch (ArithmeticException a) {
   ...>     ;
   ...> }            // <-------   compiles fine here

jshell> try {
   ...>     ;    // if I use throw new WrongInputException() it would have compiled perfectly
   ...> }
   ...> catch (WrongInputException a) {
   ...>     ;
   ...> }
|  Error:
|  exception WrongInputException is never thrown in body of corresponding try statement
|  catch (WrongInputException a) {
|  ^------------------------------...
4 Replies
JavaBot
JavaBot•3d ago
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ayylmao123xdd
ayylmao123xdd•3d ago
extend runtime exception instead of exception and see if it helps
straightface
straightface•3d ago
its because when you extend with Exception its a checked exception and it must be thrown in body somewhere and because its also parent class of RuntimeException aka unckecked exception it allowed to compile since RE can't be checked for
JavaBot
JavaBot•2d ago
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