If you do have a performance problem, then measure, don’t guess.Of course this can be true in the opposite direction too. What might seem inefficient beforehand, can easily turn out to be performant in practice. Finally, consider the load of k in our loop, which is a candidate for. You should not optimize for performance unless you have a performance problem that you can measure. unused and the code is dead is more difficult in the case of multiple basic blocks.Usually its in a conditional branch that logically will never be entered. Taking all these advanced and sometimes magical optimizations into account, I think it’s important to note that: 13 Answers Sorted by: 45 In Eclipse, 'dead code' is code that will never be executed. Besides, sometimes it’s really hard to squeeze the desired behaviour out of the JVM due to it’s complexity, so if you are planning to discover them yourself, be sure to be prepared for challenges. It may be some condition, loop or any file which was simply created but wasnt used in your project. Although many presentation has long lists about what optimizations are implemented in modern JVMs, for certain ones there are surprisingly low amount of documentation available. Dead code is any code which will never be executed. While the functionality won't change, it will improve the internal qualitythe quality of the source code. You can significantly improve a program's quality by removing dead code. The opposite of dead code is live, operational code. It’s really fun to dig into the details of the underlying mechanics, but it’s a bit tiresome as well. What is Dead Code The unreachable code in method 2 is called Dead code. Dead code means unnecessary, inoperative code that canand shouldbe removed. In the following program, the expression related to the result variable is loop invariant, as it’s guaranteed to have the same outcome for every loop iteration.

Back to the Optimization Playground Code motionĬode motion is a technique to relocate parts of the code from hot paths, attempting to make them execute fewer times.Įxpression hoisting is a form of such optimization, where an expression is pulled up in the execution graph, for example by moving the body outside of a loop without changing the semantics of the code. The condition j<1 is satisfied since you have written j-, change it to j++ and you should be fine. When i1, j0 and after executing the loop once, J is decremented, and thus j becomes - 1. Thanks for helping me I didnt know Java had ForEach-loop, thats cool to know :D gloriousCatnip. The reason behind your failure is the inner loop variable change. However, this does not work at all and Eclipse says that the i++ part is supposedly dead code (and this supposedly means that the code. For now, I’d like to continue with the measurements part of the previous post with more optimizations, and share my recent experiences with You. Not sure where I got the termination condition paradigm from.

Dead code java for loop