Try it. Use the System.nanoTime method before and after a method call, and see whether it makes any difference.
Use the javap tool with the -c option to print out the bytecode, and see whether there is any difference.
If the value for the final variable is a primitive or String literal, or a String that is created by appending primitives and String literals (a.k.a. compile time constants), those will be inlined. For example:
All three will have all their references replaced by their value. For instance, System.out.println(s2) will actually be compiled as System.out.println("13Hello481.0").
If the final variable is constructed using anything else, including the results of any method, then the above does not hold.
The general rule that most programmers SHOULD live by is this:
Write code that makes sense, that does what you need, and is simple.
ONLY then, if you have a performance issue, should you consider optimizing it. and then, use a tool to find out where the slowdowns are. 99.9% of the time, the slowdown is somewhere you are not looking, and you can spend hours changing one thing to gain practically nothing, while making a modest change somewhere else could give HUGE boosts.
There are only two hard things in computer science: cache invalidation, naming things, and off-by-one errors