CODEWITHSUNDEEP
javaconstructorexceptionclass-design
Sam Eberspacher
Sam Eberspacher

Reputation: 101

Why does Exception take Throwable as a constructor parameter instead of Exception?

I noticed recently that Exception has several constructors which take Throwable as a parameter. Throwable has two subclasses, Error and Exception, and generally all documentation indicates that you should not attempt to catch or handle an Error. Therefore, I am curious why Exception takes a Throwable as a constructor parameter instead of an Exception. This implies that an Exception could be created with an Error as its cause and could be handled by the application. Why is this the case?

Should custom Exception classes then only provide constructors that take Exception as parameters?

Upvotes: 9

Views: 1592

Answers (2)

engma
engma

Reputation: 1959

IMHO, Exception class constructors accept Throwable as a parameter because some libraries or APIs might need to create their failure type that extends Throwable, and then your failure handlers would need to be able to deal with those as well.

Also, you can throw a Throwable and not necessarily an Exception. This makes it easy to throw something that is a custom type of program failure, and hence it will have its unique level of recoverability.

For your custom Exception classes, I think it depends on the granularity you want when handling failures. The convention would be gracefully handled Throwables. This is because even though you may not be able to recover from an error, you may still want to notify users that it happened.

Upvotes: 4

M A
M A

Reputation: 72854

I guess it's basically because:

  1. it's not recommended to handle an Error but it's not forbidden.

  2. it's a good practice to program to the interface anyway, so the parameter type should support the widest range of types by having it as the root interface Throwable.

Upvotes: 4

Related Questions