String concatenation performance problem

Hey Guys!
I want to know the difference between

Is line 2 better in performance than line 1 or they are same? Should one use StringBuffer for cases like line 2.

Thanks!
Martin

A few things.

First the code you wrote looks like VB, not Java.

Performance, in situations like your example, should be looked at with a profiler after the code is finished.

The compiler will probably optimise some of that away, unless they are all actually variables rather than literals.

After all that I really don't think there is much of a differance.

As far as speed, I don't know that there is any difference. However, both of these examples will use much more space than StringBuffer will. To understand why, let's look at the second example:

First a new String "12" is formed from "1" + "2". Then the String "123" is formed by concatenating the "3", and so on. So overall 60 Strings will be created, one for each of the individual numbers and one for each of the intermediate results of the concatenation. On the other hand StringBuffer will use a single buffer and concatenate the characters to it dynamically.

Layne

Originally posted by Steven Bell:
A few things.

First the code you wrote looks like VB, not Java.

I think the above was meant as pseudocode. With only a little fleshing out, it would be perfect Java.

Layne

Note: If you're really worried about performance (and not worried about thread synchronization), then Java 1.5's StringBuilder is intended to be even more efficient than StringBuffer.

Don't forget compiler-optimization!
using once:

and another time:

results in exactly the same class.

Using Stringbuffer (or ~Builder) is mostly the better solution, together with a loop, since it is more easy to modify.