Java

Tail recursion can be a very elegant way to solve problems that involve a significant number of iterations but are better organized using recursion, without paying the cost you normally pay for recursion. Kotlin can enable the use of tail recursion. To understand the benefits of this, a quick recap would be of value.

As most Java programmers know, Java generics are erased at compile-time. This has trade-offs, but the two main reasons for this are:

• Compatibility - Java 1.4 and earlier dealt exclusively in raw types at the VM level. Generics were able to compile without introducing significant new typing to the bytecode and classfile format spec, and having to deal with older classes generated without that typing.
• Simplicity - By erasing to raw types, the JVM doesn’t have to understand specialization; something that has its own complexities and downsides. For example, specialized types are much more challenging to optimize with a just-in-time compiler.

However, knowing the type parameters used at runtime can have real value, and it’s something Java simply doesn’t offer. Kotlin would like to help in this area, but there are many challenges in doing so.

One of Kotlin’s strengths is that generally speaking, the code you might write in Java is generally more compact in Kotlin without losing any of the readability, functionality, or performance.

An odd case where that doesn’t prove to be true is declaring loggers as Java developers.

This year at JVMLS, Brian Goetz talked about Pattern Matching on the JVM and how it might be modeled. In particular he spoke about:

• How Scala does it
• How C# does it
• How Java might do it
• How Java could do it with amortized constant-time Matching

Today’s Kotlin library article is about the kotlin.concurrent package, and everything that adds to the platform.

Java’s concurrency package is already quite sophisticated, and rather than re-invent so many extremely delicate abstractions, the Kotlin authors focused on making the libraries better suited to the language by decorating and shortening various features.