Disambiguating empty catch blocks

[Marek Kozieł]

2010/4/13 Bruce Chapman <brucechapman at paradise.net.nz>:
> Empty catch blocks are ambiguous and can mean one of
>
> - I want to ignore this exception - the code works correctly when the catch
> block executes.
> - I know that this exception will never actually occur in this particular
> case - the catch block never executes.

Hello,
Some time ago I was thinking same about it, but
You can do ignore with static import which can be added do base
library, while adding method to exception is not possible.

Exceptions that will never actually occur mean that Java is in lack of smf.
Maybe you will find my way of thinking as interesting:
http://lasu2string.blogspot.com/2010/02/forwarding-as-language.html
but I doubt that any will be don about it. ^___^

-- 
Pozdrowionka. / Regards.
Lasu aka Marek Kozieł

> - The catch block is incomplete - a bug.
>
>
>
> To enable programmers to disambiguate these situations I propose adding the
> following methods to Exception:
>
> /**
> This method does absolutely nothing. Calling it in a catch clause can be
> used to explicitly indicate that the exception itself is being deliberately
> ignored.
> */
> public void ignore() {
> }
>
>
>
> and
>
>
>    /**
>    This method throws an AssertionError with this Exception as its
>    cause.
>    @throws an AssertionError
>    */
>    public void impossible() {
>        AssertionError aPaddy =
>            new AssertionError("The impossible happened");
>        aPaddy.initCause(this);
>        throw aPaddy;
>    }
>
>
>
> example:
>
>    byte[] rawMessage= ...;
>    String msg = null;
>    try {
>        msg = new String(rawMessage,"UTF-8");
>    } catch (UnsupportedEncodingException e) {
>        e.impossible();
>    }
>
> These two methods provide a means to make the programmer's intent explicit
> for the first two meanings of an empty catch block and satisfies tools (IDEs
> and static anaylsis) that the catch block isn't just declaring an unused
> variable, thus enabling a more robust interpretation of an empty catch block
> (or unused exception variable in a catch block)  as a problem to be
> rectified.
>
>
>
> Some questions:
>
> Is Exception the right home for this, or is there any value in hoisting it
> into Throwable?
>
> Any problems which I have overlooked?
>
> Comments?
>
> With a little encouragement (like someone offering to mentor this), I will
> file an RFE for this, and start work on a changeset against openJDK7 to
> implement it. Yes I realise that the javadoc needs a little more
> development.
>
> regards
>
> Bruce Chapman
>
>
>
>