jmh VS jdk7u-jdk

JMH for benchmarks

I would recommend using JMH instead.

Reflection is probably very roughly between 10 and 1000 times slower. Why don't you measure it yourself using JMH?

Aleksey Shipilev is another such leader, whom is especially knowledgeable about the internals of the JVM. His writings are invaluable. He is (was) the lead of the Java microbenchmark framework (JMH} which is how one would write small performance experiments in Java, and learn what really makes a difference or now.

In the last episode we implemented a parallelMap operation using streams, raw threads, a threadpool with futures, and coroutines. At first glance the raw threads was quickest, followed by futures, coroutines and then streams. In this, part 56 of an exploration of where a Test Driven Development implementation of the Gilded Rose stock control system might take us in Kotlin, we investigate the performance of the different functions further, in particular digging down into why coroutines seem to be slow and finding a way to speed them up. We also find a way to use a particular ForkJoinPool to run the streams code, making it as fast as the others (bar the raw threads). Frankly we only use very rough benchmarks here, with no statistical testing except 'it looks like'. That's OK for gross differences, but is highly suspect when deciding which of two similarly performant approaches is faster. For that check out JMH and you could watch my video from KotlinConf 2017

A few months ago, we started to use JMH in our project to test and find performance issues. The tool provides multiple modes and profilers, and we found this useful for our purposes.

Skip lists are relatively simple to make lock-free, while lock-free (even unbalanced) binary search trees are an absolute nightmare.

https://github.com/openjdk-mirror/jdk7u-jdk/blob/master/src/...

Here is the JDK 7 String#hashCode(), which operates on characters: https://github.com/openjdk-mirror/jdk7u-jdk/blob/f4d80957e89....

That's changed in the newer versions, because String has a `byte[]` not a `char[]`, but it was just fine. A hash algorithm can take in bytes, characters, ints, it doesn't matter.

In Java, you don't get access to the bytes that make up a string, to preserve the string's immutability. So for many operations where you might operate on bytes in a lower level language, you end up using characters (unless you're the standard library, and you can finagle access to the bytes), or alternately doing a byte copy of the entire string.

I admit, checksums using characters are a bit weird sounding, but they should also be perfectly well-defined.

"AbstractInterruptibleChannel" seems to be doing this, and the comments/javadocs offer some hint. As to why they're designed this way, that's a good question.

https://github.com/openjdk-mirror/jdk7u-jdk/blob/master/src/...

In Java, you could use BigDecimal. I linked to the source code, because it highlights the amount of complexity you get.

The windows implementation of AWT Desktop just calls the Win32 API ShellExcute function. This then quickly descends into questions such as "what version of windows do you have"; "does it correctly understand the difference between open vs. edit"; what does your registry currently contain"; etc.

ArrayList is a class, it is not an array. It stores two values. An array and its size. You can see this if you read the source code for ArrayList.

The source code for the Java SDK is available on github.