What is the usefullness of an empty statement?

Answer 1

Generally speaking, one will find empty statements ("do nothing" statements), in one of three places:

1. As the body inside a "while" or "do-while" loop
2. As the body inside a "for" loop
3. As the first statement body in an "if..then..else" conditional (i.e the body for the "then" portion)

The first case is very bad programming (not just bad style, but bad design). There should never be an instance when you want a do-nothing body to a while or do-while loop.

The second case is usually frowned up as bad style, but there are certainly cases where it can be the proper choice. In such a case, the loop conditionals inside the for statement perform all the work, and there is no need for the body to do anything. An example would be a case where we need to find the index number of the position of a certain element that is known to be stored in an unsorted array. Here's what that would look like:

arraypos=0

for ( ; myArray[arraypos++].equals("somevalue") == false ; ) {

// do nothing

}

The third case where an empty statement is found is as the "then" body portion of an "if...then...else" statement. In this case, the do-nothing exists for readability, since the statement could easily be re-written to be just an "if...then" conditional, with the test condition negated. However, sometimes it is easier (or more understandable) to write a test condition one way, and the inverse of that being much less clear. E.g.

if ( complex_condition ) {

// do nothing

} else {

do_a_bunch_of_stuff();

}

can sometimes be clearer than

if ( ! (complex_condition) ) {

do_a_bunch_of_stuff();

}

It should be rare that this is needed, but it can help the code flow in certain cases where the logic behind the conditional is easier to understand than the inverse of that conditional.