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Nicolai Parlog

@nipafx

3 Nov

From compact record constructors to pattern matching, from generic wildcards to chaining predicates and comparators, from jpackage to jlink - here are 11 #Java tricks handpicked from dev.java. 🧵

(Musical version of this thread: )

0/11

A #record's *canonical* constructor has one arg per component but in its *compact* form, you don't have to list them. You also don't have to (in fact, can't) assign fields, just do the checks/reassignments you need, rest happens automatically.

More: dev.java/learn/using-re…

1/11

Serialization works great with #records, no black magic needed! The guaranteed presence of constructor parameters and accessors makes serialization work with the object model and makes it easy to create reliable serializable records.

More: dev.java/learn/using-re…

2/11

Read 12 tweets

Nicolai Parlog

@nipafx

16 Mar

Here are 11 improvements you get when updating to #Java16 later today: from records and type patterns to `Stream`-additions and Unix domain sockets, from creating installers to more performance and observability. 🧵👇🏾

(Longer form with tons of links: nipafx.dev/java-16-guide/)

#1 Records

Express in a single line that a type is just a collection of data without need for encapsulation and let the compiler do the rest:

record Range(int low, int high) { }

That results in almost the same API as the attached class. *drops mic*

#2 Type Pattern Matching

This is actually two-for-one:

* first step into pattern matching
* type patterns with `instanceof`

With a type pattern you check whether a variable is of a certain type and, if so, create a new variable of that type, so you can use it without casting.

Read 14 tweets

Nicolai Parlog

@nipafx

14 Mar

@chegar999

"Towards better serialization!"

That's a guiding light of #ProjectAmber and record serialization is the first step. The Inside Java Podcast episode on that topic with Julia Boes and @chegar999 (inside.java/2021/03/08/pod…) gives great insight into how it achieves that. 🧵

1/10

https://twitter.com/nipafx/status/1359835273992019969

First, what's wrong with regular serialization? In short:

* extralinguistic mechanism (aka "magic")
* undermines encapsulation
* causes security issues
* hinders evolving code
* holds back new Java features

In long (and why it turned out that way), see attached thread.

2/10

https://twitter.com/nipafx/status/1359835273992019969

@BrianGoetz

"The magic is where the sin was" (@BrianGoetz) and so record serialization promises "what you see is what you get", making it:

1. easy to understand
2. no magic
3. more secure
4. more performant

3/10

Read 10 tweets

Nicolai Parlog

@nipafx

12 Mar

Do you dream of "value types" in Java? So do I! Hence I was thrilled to see that Project Valhalla is slowly coming out of exploration with two draft JEPs.

Here's what they currently propose. 🧵👇🏾

(If you prefer video: https:/www.youtube.com/watch?v=WBvTilbh8S0&t=344s)

1/10

First, why value types? To bridge the divide between

* primitives (fast, no memory overhead) and
* reference types (abstraction, safety, identity)

As is, we sometimes have to choose between performance and design. And we often choose wrongly.

2/10

Draft JEP openjdk.java.net/jeps/8251554 proposes new terminology and JVM rules:

1. Interface `IdentityObject` (the boring part):

* for reference types
* called "identity classes"
* instances are "identity objects"

For identity classes / reference types everything stays as is.

3/10

Read 10 tweets

Nicolai Parlog

@nipafx

11 Feb

@BrianGoetz

"When people ask me what feature do I most regret, serialization is the easy answer" - @BrianGoetz

Let's talk about serialization in Java: Why does it exist? What are the problems (even today)? Would Java have been better off without it? Can it be fixed?

1/11

NB: What follows is mostly quotes or paraphrasing from a conversation I had with Brian during my 25-hour live stream. If you want to watch the full discussion about serialization, nullability, primitives, and more, you can find it here:

2/11

Serialization was introduced because turning an object graph into bytes is valuable: You can store things on disk, in databases, or send them over the wire. But while the concept is sound, it was implemented in a horrible way.

"I wasn't on the team at the time" - Brian

3/11

Read 11 tweets

Nicolai Parlog

@nipafx

27 Jan

Project Amber is making progress on pattern matching in #JavaNext. Here are three recent developments that I'm very excited about and I think you will be as well.

(Caveats: these are ongoing discussions; none of this is final; speculation and strawman syntax ahead)

1. "Array patterns" allow matching and destructuring arrays. The `if`-line does three things:

a) is `objects` a `String` array with length 2?
b) if so, cast it to `String[]` and extract the two elements
c) declare `a` and `b` and assign the two elements to them

"Can I also bind the arrays as a whole?"

Likely. This is called an "as pattern".

"What if the array can have more elements?"

Allowing to express "at least two elements" is being considered - for example with three dots.

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