switch expression can't be float, double or bo

Question

Why doesn't the switch expression allow long, float, double or boolean values in Java? why is only int (and those that are automatoically promoted to int) allowed?

Answer 1

Float and double would be awkward to use reliably even if they were possible - don't forget that performing exact equality matches on float/double is usually a bad idea anyway, due to the nature of the representation.

For Boolean values, why not just use if to start with?

I can't remember ever wanting to switch on any of these types, to be honest. Do you have a particular use case in mind?

Answer 2

For float and double float and double I'd assume they have omitted it for the same reasons as why it's a bad idea to compare them using ==.

For boolean, it may simply be because it would correspond to an if statement anyway. Remember that you can only have constants in the case-expressions, so the cases would always correspond to if (someBool) and if (!someBool).

For long I don't have an explanation. Seems to me that such feature perhaps should have been included when designing the language.

Answer 3

Usually switch-case structure is used when executing some operations based on a state variable. There an int has more than enough options. Boolean has only two so a normal if is usually good enough. Doubles and floats aren't really that accurate to be used in this fashion.

Frankly I can't imagine a use case for this stuff, did you have some practical problem in mind with this question?

Answer 4

You can use enum in a switch statement and Java 7 will add String AFAIK. The switch statement comes from C where only int's were allowed and implementing other types is more complicated.

Floating point numbers are not a good candiates for switch as exact comparison is often broken by rounding errors. e.g. 0.11 - 0.1 == 0.01 is false.

switch on boolean is not much use as a plain if statement would be simpler

if(a) {

} else { 

}

would not be simpler with

switch(a) {
  case true:

     break;
  case false:

     break;
}

BTW: I would use switch(long) if it were available, but its not. Its a rare use case for me any way.