Interesting Links – 17 Oct 2016

  • JEP 295: Ahead-of-Time Compilation offers deployers a chance to compile the base Java modules to native code. This can save time on some optimizations, but it’s understandably limited (and should be).
  • The Halstead Metrics (also known as “Halsted metrics”) discusses code complexity in Java. Worth considering; this particular explanation comes courtesy of JHawk, a commercial code metrics tool, not to be confused with “j-hawk“, an open source testing tool.
  • Experimenting with “mutation testing” and Kotlin is a neat post describing PIT, a testing tool that changes your source code and runs your tests – if your tests don’t fail, your tests are probably bad (or your code’s awful.)

Interesting Links – 5 Oct 2016

  • In Accounts is Everything Meteor Does Right, Pete Corey points out that Meteor‘s Accounts package dictates how user authentication and authorization will work, period, and that this removal of choice actually makes it entirely usable. Having wrestled with Shiro and Crowd and Spring Security and JAAS, it’s a point that’s hard to argue with – and while users of Shiro, etc., will probably say that those packages work as well as Accounts does, I’d have to humbly disagree, even while acknowledging how nice it is to have things like Shiro and Crowd. It’d be nice to have something that was just as drop-in for Java was Accounts is for Meteor. (Meteor is, BTW, a reactive application framework for NodeJS.)
  • User jdlee posted Maslow’s hierarchy of dev needs from Twitter – One gets the impression that the developer’s needs weren’t being met when designing that graph.
  • Also from jdlee, who was apparently crawling Twitter: “In Ruby, everything is an object. In Clojure, everything is a list. In Javascript, everything is a terrible mistake.”
  • User adimit gave high praise to Growing Object-Oriented Software Guided by Tests, saying that “it’s really simple but helping me write a test-driven app right now” and (coming from a Haskell background) “I’ve always hated OOP, but now I see how to do it properly, and it can be fun.” Anything that helps code quality improve is awesome, if you ask me.
  • From DZone: The Rise and Fall of Scala describes the apparent slow demise of Scala. The author backs it up, and it’s not a bad article; Scala’s awesome (I love it) but the criticisms are quite valid. Two areas where the author sees Scala remaining strong: Big Data and custom DSLs, definitely two Scala strengths.

Interesting Links – 3 Oct 2016

  • User MarkyC showed Falsehoods Programmers Believe About Phone Numbers, in response to a query about what data types were useful for storing phone numbers. Channel consensus was to do what was necessary, but usually: String.
  • From Reddit, OpenJDK6 End of Life details how the open source OpenJDK6 is reaching its end of life, years after the official Java 6 and Java 7 have reached theirs. This was surprising; I didn’t realise OpenJDK6 was still maintained at all.
  • Maven Wrapper is a project that provides mvnw – an analog to Gradle‘s gradlew, a command that will download a Maven instance local for the project. Thus, users of the project don’t have to download or install Maven to be able to run it. (It may or may not work; feel free to try it out!)
  • User ernimril mentioned creative branching via Befunge – you can find an interpreter for it in Java here. Cool stuff, with a more family-friendly name than, say, some other languages that I won’t mention here. (Note paralipsis, used ironically and against my better judgement.)
  • Only works on Windows, but MobaXterm looks cool. Might help alleviate the Microsoftitis that many still suffer from. Has a free edition and commercial edition; some devops people recommend it highly.

Interesting Links – 29 Sep 2016

  • The reflections project scans your classpath, indexes the metadata, allows you to query it on runtime and may save and collect that information for many modules within your project.
  • “try { return } finally {}” demonstrates what happens when a finally block modifies a reference that’s being returned in the try block. It’s rather interesting.
  • Need to generate fake data? https://github.com/DiUS/java-faker to the rescue. It’s a port of a popular Ruby GEM; this is not the only implementation, but it serves.
  • User Anthaas offered this gem: “You’ll find most of the people who waste a large amount of time on something simple do so because they are fixated on fixing their solution, rather than finding a solution that works.”
  • User liste pointed out JSimpleDB, a project that says it is a “a better persistence layer for Java.” Basically, it provides a transactional access layer for various data stores (SQL databases, NoSQL data stores) as key/value stores, with quite a laundry list of features copied from the project home page:
    • Encoding/decoding of field values
    • Enforcing referential integrity; forward/reverse delete cascades
    • Field indexes (simple and composite)
    • Query views
    • Schema management
    • Change notification
    • Validation queues
    • Command line interface
    • Designed from the ground up to be Java-centric; 100% type-safe at all times.
    • Works on top of any database that can function as a key/value store (SQL, NoSQL, etc.)
    • Scales gracefully to large data sets; no “whole database” operation is ever required
    • Configured entirely via Java annotations (only one is required)
    • Queries are regular Java code – there is no “query language” needed
    • Change notifications from arbitrarily distant objects
    • Built-in support for rolling schema changes across multiple nodes with no downtime
    • Supports simple and composite indexes, including on user-defined custom types
    • Extensible command line interface (CLI) including Java 8 expression parser
    • Built-in Java-aware graphical user interface (GUI) based on Vaadin

Interesting Links – 26 Sep 2016

  • Oh, shit, git! is a site that shows a number of common things git users say, as well as how to fix the situations that cause them. Note that the title indicates that the readers are expected to be of age. Some examples:
    • Oh shit, I did something terribly wrong, please tell me git has a magic time machine!?!
    • Oh shit, I committed and immediately realized I need to make one small change!
    • Oh shit, I need to change the message on my last commit!
    • Oh shit, I accidentally committed something to master that should have been on a brand new branch!
    • Oh shit, I accidentally committed to the wrong branch!
    • Oh shit, I tried to run a diff but nothing happened?!
    • F*ck this noise, I give up.
      It’s worth noting that your editor has used at least a variant of all of these statements, most of them even in recent memory.
  • User whaley, in a moment when he wasn’t accompanied by roosters, cows, and goats, pointed out “Suffering-oriented programming“, saying that it convinced him that “make it work, make it pretty, make it fast” is the right approach, as compared to “make it work, make it fast, make it pretty.” Good read.
  • From Reddit: “Recaf is an open-source framework for authoring extensions (dialects) as libraries for Java. You can redefine every major syntactic element of the language, either add new ones or create your own flavor of Java that matches your needs. It can be used to give syntactic support to libraries, to generate and instrument code. Last but not least you can experiment with the design and implementation of Java extensions in plain Java.” Seems like another tool to compete (sort of) with Lombok and Autovalue.

Interesting Links, 15 Sep 2016

  • It may be a little early to suggest that Eclipse is dead, but “The Fall of Eclipse” says it anyway, and says why. The Eclipse community would disagree, of course.
  • User liste pointed out MariaDB4j, which is… MariaDB embedded into a jar, suitable for integration testing with MariaDB in a build tool. Sure, H2 and Derby exist, but this allows you to test against MySQL and MariaDB, because if you have to use MySQL in whatever terrible world you happen to live in, you definitely want to test against it instead of a good database, to help you work out what awful bugs you need to avoid.
  • User yawkat also pointed out something that your humble author was unaware of: the hash code of Java Strings isn’t calculated until hashCode() is called. That makes perfect sense, actually. The javadoc for String’s hashCode() points out how the hashcode is calculated, but not when.
  • User cheeser pointed out O’Reilly’s (legal and free) Data Ebook Archive: “An archive of all O’Reilly data ebooks is available below for free download. Dive deep into the latest in data science and big data, compiled by O’Reilly editors, authors, and Strata speakers.”
  • The channel has mentioned tries (pronounced “trees”) as a form of data structure a few times lately; in case you don’t know what a trie is, or how it differs from a tree, see The Trie: A Neglected Data Structure.
  • Using NPM (Node.js‘ package manager) as part of a Java build came up one morning. Without any further context, here are a few references show up to integrating NPM into a maven build, none of which has been tried and tested by the person writing this up for you:

Interesting Links, 2016 Sep 13

  • Technical Itch: JVM guaranteed safepoints, Safepoints in HotSpot JVM, and Dynamic Deoptimization came up in conversation.
  • javap.yawk.at – selckin says it’s basically “take a peek under the hood at the java bytecode for fun and profit.” Interesting site, though, it basically runs javap and procyon (a java decompiler) over submitted code and shows you the bytecode and associates it with the lines of java (or kotlin, or scala) that generated that bytecode.
  • NetBeans Proposal suggests a migration of NetBeans (possibly a fork?) from Oracle to Apache, opening up NetBeans to Apache’s governance model and a wider community. Considering the noises Oracle’s made around NetBeans being deprecated (and therefore likely abandoned), this sounds like a great idea.

What you want to have to develop Java

Recently a user asked what they would need to know to develop a “small web application” using Java, including a database.
This is not a good question, really, but IRC user surial gave a lot of relevant information that’s worth preserving and adding to. This is not what surial said – if you’re interested in the actual content, see the channel logs – but this is a paraphrase that attempts to build on surial’s information.

What you need to develop in Java

Java

If you’re going to develop in Java, you obviously (hopefully) need Java itself. You want the JDK, not the JRE (the JDK includes the JRE.) You can use the official Oracle JDK, OpenJDK (from Red Hat, if only for more than Linux support), or Zulu – and this is not likely to be an exhaustive list by any means.
The Oracle JDK is different from OpenJDK only in some of the libraries included. Notably, the JPEG encoder is closed source, so OpenJDK’s JPEG support is not part of OpenJDK itself. Other builds may not have the same problem.
If in doubt, use Oracle’s JDK. There’s nothing wrong with OpenJDK, but when people mention the JDK, they usually mean the official JDK in terms of features and support.
One word about versions: use Java 8. Older versions have already been end-of-lifed, even though they’re still available through archives.

An Editor

Want to start a war? Make a firm recommendation for a development environment, and insult the other environments. The truth is, Java uses text as source; use what works for you.
Popular choices for development environments are IDEA (with both commercial and free versions, although people think of the commercial versions first), Eclipse (also with commercial and free versions, where people think of the free versions first), and Netbeans (with free versions and probably some commercial versions hanging out somewhere.)
All three are quite capable in their own ways. Eclipse is famous for having a perspectives-driven approach, where IDEA and Netbeans are more traditional. They all have free versions; try them out and see what works for you.
Of course, there’s nothing preventing you from using any other editor, either: Sublime Text, Atom, Brackets, vim, emacs, or anything else that can generate text.

A Build System

Strictly speaking, you don’t have to have a build tool. You could always compile manually, by typing javac, after all, and save yourself some work by maybe using a batch file.
Or, if you’re using a Java IDE like IDEA, Eclipse, or Netbeans, you could always use the IDE to build your project. In practice, your IDE will be compiling your project if only to run local tests and tell you about issues in your code, after all.
However… what you should be using is one of Maven, Gradle, SBT, or Kobalt (probably in order of desirability, and as with the other lists in this article, this is not exhaustive).
These build systems allow you to write a configuration that describes your build in such a way that the build is portable to other systems, including integration servers and, well, other users. If you rely on a batch file, you’re hoping that their filesystem and operating system match yours; if you rely on an IDE, you’re hoping that others use the same tools you do.
They don’t. Even if they do, they don’t.
A build system includes the ability to manage dependencies (the libraries your application might use) and other such things, and will also provide the ability to run tests automatically as part of your build process.
Each build system’s configuration can either be loaded by an IDE, or can export an IDE configuration, so you can use any IDE without worrying about the project.
In real terms: use Maven unless you have some process that you need fine-grained control over; if you do need fine-grained control over your build, use Gradle. If you’re using Scala, use SBT. If you’re interested in a new build tool’s development, try Kobalt. Don’t use Ant, make, or CMake, and for goodness’ sake don’t use javac directly after “Hello, World.” You’re not a barbarian.

Talking to a Database

If you’re working with a relational database (and you probably are, if you’re working with persistent data), you have a few ways to go: SQL (where you use JDBC to talk to the database in its own variant of SQL), object-relational mapping (where you use a library that manages data as if it were represented natively as Java objects), or a bridge between the two, where you sort of get objects but you are still thinking relationally.
Examples of ORM libraries: Hibernate and EclipseLink. You can use the JPA standard with either, although Hibernate has a native API that’s arguably more powerful. (EclipseLink probably does, too, but your author has no experience with EclipseLink’s native API, if it has one.) Note also that object-relational mapping is… imperfect. You’re gaining a lot by using Java’s data structures… and you’re losing some because those structures usually don’t map perfectly to a relational model.
Examples of others: jOOQ (“the easiest way to write SQL in Java,” according to their website), JDBI (“convenient SQL for Java”), and Spring Data (a flexible abstraction in front of nearly any persistence mechanism) – your mileage with each may vary, but they all seem to be pretty highly regarded.

Libraries

The Java ecosystem is one of Java’s greatest strengths. The nice thing about having a build tool is that it’s trivially easy to leverage the Java ecosystem, by simply specifying the “address” of a library, and then having the library and its dependencies included in your build by virtue of your build tool’s dependency management.
So: which libraries do you want to use?
There’s no real answer to that: “the ones you need” are probably the best candidates, and generally experience is how you learn which ones you need. Google searches for “java json parser” will give you workable answers for JSON parsing in Java, although they might not be the best answers – feel free to ask the ##java channel or its bot for suggestions on functionality.
However, here are some common libraries that many projects use without worrying about technical debt:

  • Guava (generalized utility library)
  • Lombok (annotations to reduce boilerplate with no runtime dependencies)
  • TestNG or JUnit (testing frameworks)

Quickstarts

If you need to get your project moving quickly, ##java has at least two quickstart projects ready for use, with a small amount of work.
If you want a Gradle project, see https://bitbucket.org/marshallpierce/java-quickstart.
For a Maven quickstart, see https://github.com/jottinger/starter-archetype.

Interesting Links, 14 April 2016

  • Natty is a natural language date parser written in Java. The idea is that you feed it corpora like "1984/04/02", "february twenty-eighth", or "3 days from now", and get back a list of potential matching Date objects. It is not designed to pull dates out of natural language – for that you’d want something like OpenNLP – but it might be able to help convert the natural language dates you get from OpenNLP into Java’s Date representations.
  • Scriptus is a Maven plugin that writes the Git version into build properties. It’s not entirely well-documented, but that’s what open source might be able to fix, right?
  • In When Interviews Fail, Ted Neward deconstructs a DZone article (“Can You Call Non-Static Method From a Static?“). It’s not difficult to imagine the activity – after all, this site does it to authors all the time! – but Ted’s especially good at it. In this case, he’s actually trying to dig at the purpose of an interview in the first place – and closes with “what do you really interview for?”, because if you’re interviewing for some grunt who can answer the corner cases, that’s… all you’re going to get.
  • The jOOQ blog asks: “Would We Still Criticise Checked Exceptions, If Java had a Better try-catch Syntax?” History says that yes, people would criticize Java for pretty much anything they can think of, and a few things they can’t. But in this case, it’s talking about potential syntax where the try is optional. It’s not present in a real compiler, and it does have some syntactic clarity to it – but in this author’s opinion, it’s actually hiding some pretty important information (namely, that you’re entering a try/catch block, which is pretty relevant information.)
  • From DZone: Properly Shutting Down An ExecutorService shows us a Spring bean to manage an ExecutorService shutdown. This, in itself, is a good thing. However, the interesting thing is that he wrote this because Tomcat was failing to kill the ExecutorService itself – he’s basically illustrated why doing thread management in a web application is a bad idea. Let the container manage the threads, people. (This has always been in the specification – the apps are not supposed to start threads. Ever. Use message-driven beans, or timers, or a ManagedExecutorService.)

BTW, feel free to send me Java-related (or somewhat Java-related!) links you think are worth retaining!

Byte Order Marks (BOM)

The so-called Byte Order Mark is a special unicode character that has no visual representation. The point of it, is to start your text data with this pseudocharacter; it serves as a way to identify “Endianness” – that the text is encoded with UTF-16 (Little Endian), or UTF-16 (Big Endian), or UTF-8.
Java handles it kinda weirdly; this post describes how it works.
The BOM is the bytes: 0xFE 0xFF. That means:

Encoding First bytes in the stream
UTF-16, Little Endian FF FE
UTF-16, Big Endian FE FF
UTF-8 EF BB BF

You can use these to identify streams.
In Java, the BOM is left in the stream data. So, if you for example have a UTF-8 text file that starts with a BOM, and you read it into a String, your string starts with the BOM character. It doesn’t show up when you print it, but it still ‘counts’, in the sense that the .length() call on your string counts the BOM as 1 character, and a string that starts with a BOM is not equal to one that doesn’t start with it, even if they are otherwise the same. You probably want to filter it out!!
The only exception is the special encoding UTF-16. This encoding will, if it’s there, consume the BOM and use it to configure itself as Little Endian or Big Endian. If there is no BOM, it defaults to big endian. Note that this ‘consume the BOM’ behaviour does not apply to the encodings UTF-16LE and UTF-16BE. They read the BOM as normal.
NB: Esoteric note: The unicode character 0xFF 0xFE is intentionally defined as not valid, so that the BOM can be used unambiguously as indicating the endianness of a UTF-16 stream. However, in java, reading this special invalid character does not throw an exception. You can therefore read the byte data: FF FE 41 00, which is the string "A" encoded with a BOM as UTF-16 Little Endian using the encoding UTF-16BE. This produces garbage, but does not throw an exception.