default branch placement in switch

Kevin Bourrillion kevinb at
Mon Dec 11 18:16:11 UTC 2017

On Fri, Nov 3, 2017 at 5:25 PM, Brian Goetz <brian.goetz at> wrote:

> or plan to eventually get to a place where default always comes last, even
> for "int" switches. If we want to get to the latter, we should start
> warning on this construct now.

I favor starting to warn and eventually forbidding default in any position
but last for all constructs that have it.

A switch with the default in the middle is extremely weird and confusing.
If I'm reading code to understand what happens when i == 3, and I read as
far as

switch (i) {
  case 1:
    justOneStuff(); break();
  case 2:
    justTwoStuff(); break();

... then I immediately assume that this must be where execution is
continuing. Worse, even if I do notice that there are more case labels to
follow, and I resume searching for a `case 3:`, then when I don't find one
I now risk making *another* error and forgetting to jump *back* to the

This is kind of insane. At first I was less worried because I thought
"surely no one is actually doing this"... then I browsed our codebase....

We should at least strongly consider this.

On 11/3/2017 5:10 PM, Tagir Valeev wrote:
>> Hello!
>> Currently the default branch can be placed in any place inside the
>> switch operator, e.g. like this:
>> switch(i) {
>> case 1: System.out.println("one");break;
>> default: System.out.println("other");break;
>> case 2: System.out.println("two");break;
>> }
>> In this case behavior does not change on the order of case blocks.
>> However in pattern matching the order of cases usually matters: if
>> some pattern matches, this means that the subsequent patterns will not
>> be checked. Does this mean that with pattern matching the default
>> branch makes all the subsequent case blocks unreachable? Or default
>> can still be located anywhere and is checked only after any other
>> pattern?
>> With best regards,
>> Tagir Valeev

Kevin Bourrillion | Java Librarian | Google, Inc. | kevinb at
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