Is there an beautiful way to assert pre-conditions in Java methods?

Question

A lot of my functions have a whole load of validation code just below the declarations:

if ( ! (start < end) ) {
    throw new IllegalStateException( \"S         


        

Answer 1

Guava's Preconditions class is just for this. You typically use it with static imports, so your example would look like:

checkArgument(start < end, "Start must be before end");

It makes it easy to add more information to the message as well, without paying the cost of String concatenation if the check passes.

checkArgument(start < end, "Start (%s) must be before end (%s)", start, end);

Unlike assert statements, these can't be disabled.