Exception handling in java using finally

Question

public class CheckProg {
    public int math(int i) {
        try {
            int result = i / 0;
       // throw new IOException("in here");
        } catch (Exception e) {
            return 10;
        } finally {
            return 11;
        }
    }
    public static void main(String[] args) {
        CheckProg c1 = new CheckProg();
        int res = c1.math(10);
        System.out.println("Output :" + res);
   }

Question: If I run the above code, I get the result as Output: 11

Why? Shouldn't the exception be caught before in the catch block and returned?

Answer 1

Shouldn't the exception be caught before in the catch block and returned ?

It is being caught, and that return statement is being executed... but then the return value is being effectively replaced by the return statement in the finally block, which will execute whether or not there was an exception.

See JLS 14.20.2 for details of all the possibilities. In your case, this is the path:

If execution of the try block completes abruptly because of a throw of a value V, then there is a choice:

• If the run-time type of V is assignment compatible with a catchable exception class of any catch clause of the try statement, then the first (leftmost) such catch clause is selected. The value V is assigned to the parameter of the selected catch clause, and the Block of that catch clause is executed. Then there is a choice:

  • If the catch block completes normally [ ... ignored, because it doesn't ]

  • If the catch block completes abruptly for reason R, then the finally block is executed. Then there is a choice:

    • If the finally block completes normally [ ... ignored, because it doesn't ]

    • If the finally block completes abruptly for reason S, then the try statement completes abruptly for reason S (and reason R is discarded).

So that bottom line is the important one - the "reason S" (in our case, returning the value 11) ends up being the way that the try statement completes abruptly.

Answer 2

Yes. But the finally block is always executed afterwards and overrules the return value!