How to use final in a multi-catch statement?

Question

How to give final modifier to the exception when catching multiple type of exceptions in a single catch block in Java

Answer 1

You don't need to mark every exception as final. Just the first one.

try {

} catch(final IllegalArgumentException  | ArrayIndexOutOfBoundsException e) {
    e = new RuntimeException();//this will not be allowed as e is final
}

That being said, you don't need to mark e as final as it cannot be reassgined in the catch block either way when using a multi-catch statement.

Here's the relevant section of the JLS

An exception parameter of a multi-catch clause is implicitly declared final if it is not explicitly declared final.

It is a compile-time error if an exception parameter that is implicitly or explicitly declared final is assigned to within the body of the catch clause.

Answer 2

The following is aimed to provide the authoritative answer.

Java Language Specification, Java SE 7 Edition, §14.20:

An exception parameter of a multi-catch clause is implicitly declared final if it is not explicitly declared final.

As for the syntax:

CatchClause:
    catch ( CatchFormalParameter ) Block
CatchFormalParameter:
    VariableModifiersopt CatchType VariableDeclaratorId

This means that you can apply a single final in front of the catch type (which, in the case of multi-catch, is specified as a union of individual exception types). Your confusion may be with the fact that a multi-catch does not contain several, but just one catch variable declaration.