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Which one is faster in java ?
a) for(int i = 100000; i > 0; i--) {}
b) for(int i = 1; i < 100001; i++) {}
I have been looking for explanation to the answer which is option a, anyone? any help is appreciated
There are situations when a reverse loop might be slightly faster in Java. Here’s a benchmark showing an example. Typically, the difference is explained by implementation details in the increment/decrement instructions or in the loop-termination comparison instructions, both in the context of the underlying processor architecture. In more complex examples, reversing the loop can help eliminate dependencies and thus enable other optimizations, or can improve memory locality and caching, even garbage collection behavior.
One can not assume that either kind of loop will always be faster, for all cases – a benchmark would be needed to determine which one performs better on a given platform, for a concrete case. And I’m not even considering what the JIT compiler has to do with this.
Anyway, this is the sort of micro-optimizations that can make code more difficult to read, without providing a noticeable performance boost. And so it’s better to avoid them unless strictly necessary, remember – “premature optimization is the root of all evil”.