We've seen many Java code snippets that suppose to improve some performance. In many cases, there was NO real improvement with the additional code. Instead, the code gets bigger for no real reason.

With this project we will try to bust or prove some common performance myths.

It is not easy to write micro-benchmark code. Fortunately (and finally), we have an excellent tool for that: JMH.

Each benchmark suite is stored in a single class with a name that must end with Benchmark. Every benchmark class explains in java docs what the goal is, i.e. what is going to be measured and why. Each benchmark suite should have at least two individual benchmark methods.

Moreover, each java doc will also contain the actual benchmark results.

Easy :) The project is using Gradle. Benchmarks may be run just by passing the bechmark class name. Since class name must end with Benchmark, Gradle will recognize it and run it. For example:

gradlew clean FooBenchmark

Running clean task first is optional.

When running benchmarks, try not to use your computer for anything else. Try to minimize the number of background tasks.

Values of individual benchmark are not relevant! What matter is the relationship between the individual benchmarks and the standard deviation of the values. Only by comparing the benchmark values we can say if one has better performance then the other.

Don't take results as written in a stone. Think! Sometimes the input values (volume and the content) dictates the performance results.

Feel free to add your own benchmarks. Let us know if you want us to measure something.

Java benchmarks - the answers on common performance concerns!