Which of these pieces of code is faster in Java?

Question

a) for(int i = 100000; i > 0; i--) {}

b) for(int i = 1; i < 100001; i++) {}

The answer is t

Answer 1

Typically real code will run faster counting upwards. There are a few reasons for this:

• Processors are optimised for reading memory forwards.
• HotSpot (and presumably other bytecode->native compilers) heavily optimise forward loops, but don't bother with backward loops because they happen so infrequently.
• Upwards is usually more obvious, and cleaner code is often faster.

So happily doing the right thing will usually be faster. Unnecessary micro-optimisation is evil. I haven't purposefully written backward loops since programming 6502 assembler.