Java switch cases: with or without braces?

Consider the following two snippets, with braces:

switch (var) {
  case FOO: {
    x = x + 1;
    break;
  }

  case BAR: {
    y = y + 1;
    break;
  }
}

Without braces:

switch (var) {
  case FOO:
    x = x + 1;
    break;

  case BAR:
    y = y + 1;
    break;
}

I know that, in the snippet with braces, a new scope is created by enclosing each case in braces. However, if each case does not need the new scope (i.e. no variable names are being reused), is there any sort of performance penalty for using the braces with a case?

Solution 1:

is there any sort of performance penalty for using the braces with a case?

None.

The curly braces are there to help the compiler figure out the scope of a variable, condition, function declaration, etc. It doesn't affect the runtime performance once the code is compiled into an executable.

Solution 2:

No performance penalty from an execution point of view.

Slight performance penalty from a compiling point of view as there is more to parse, but if anyone were actually that concerned about it they would have to write their code all on one line :-)

And now for the opinion part of our post... I always put in the { and } because there is a penalty for maintainability in that you will likely have to put them in at a later date, and it can be a pain putting them in later... but that is 103% personal preference.

Solution 3:

As we know braces for switch cases are not necessary. Using braces cases may cause a confusion about the scope of a case.

An opening brace is generally associated with something meaningful like a start of a function or start of a loop or start of class declaration or start of array initialization etc...We know that, a case breaks out of switch block when it encounters a break statement. Thus using curly braces seems to imply idea of a different scope for case to an ignorant reader. So, its better to avoid using curly braces for the sake of better programming readability.

i.e. When I have something like,

switch(i)
{
  case 1 :
  {
     //do something
  }
  System.out.println("Hello from 1");

  case 2: 
  ....
}

"Hello from 1" gets printed. But use of curly brace may suggest an ignorant reader that the case ends with '}', already knowing what curly braces generally signify in case of loops, methods etc.

Like we have jump-to-label statements in 'C' the control just shifts to case and continues it's execution. So, with that understanding it's just a BAD practice to use curly braces when writing cases for switch.

Technically speaking you can surround any block of your code with an additional pair of curly braces when used with valid syntax. Using braces in switch looks so bad at least to me as it seems to give a different feel like I have said above.

My suggestion : Just avoid using surrounding braces for switch cases.

Solution 4:

With braces.

There are so many things that can go wrong with switch statements I try to avoid them where I can, i.e.

1. Forgetting breaks and thus having case fall-throughs
2. Forgetting a default case and thus not catching an un-catered for condition
3. Accidentally reusing variables between case statements, or worse yet, affecting a variable which IS sharing a variable between case statements.

Using braces is one way to prevent both intentional and accidental sharing of variables between case statements