Occasionally, you want to write a SQL query and fetch a hierarchy of data, whose flat representation may look like this: SELECT id, parent_id, label FROM t_directory; The result might be: |id |parent_id|label | |---|---------|-------------------| |1 | |C: | |2 |1 |eclipse | |3 |2 |configuration | |4 |2 |dropins | |5 |2 |features | … Continue reading How to Turn a List of Flat Elements into a Hierarchy in Java, SQL, or jOOQ
This fun fact has been on my mind for a while, and a recent reddit thread about "Smuggling Checked Exceptions with Sealed Interfaces" made me write this post here. Namely, Java had union types before it was cool! (If you squint hard). What are union types? Ceylon is an underrated JVM language that never really … Continue reading Java’s Checked Exceptions Are Just Weird Union Types
Java 16 includes an improvement that makes the language a bit more regular via JEP 395. The JEP says: Static members of inner classes It is currently specified to be a compile-time error if an inner class declares a member that is explicitly or implicitly static, unless the member is a constant variable. This means … Continue reading Write C-Style Local Static Variables in Java 16
I just fixed a bug. The fix required me to initialise an Object array with the init values for each type, instead of just null, i.e. false for boolean, 0 for int, 0.0 for double, etc. So, instead of just doing: Object converted = new Object[parameterTypes.length]; I needed: Object converted = new Object[parameterTypes.length]; for (int … Continue reading Could we Have a Language That Hides Collections From Us?
One of the Stream APIs greatest features is its laziness. The whole pipeline is constructed lazily, stored as a set of instructions, akin to a SQL execution plan. Only when we invoke a terminal operation, the pipeline is started. It is still lazy, meaning that some operations may be short circuited. Some third party libraries … Continue reading A Quick Trick to Make a Java Stream Construction Lazy
How to write a simple API is already an art on its own. I didn't have time to write a short letter, so I wrote a long one instead. ― Mark Twain But keeping an API simple for beginners and most users, and making it extensible for power users seems even more of a challenge. … Continue reading How to Write a Simple, yet Extensible API
Annotation processors can be useful as a hacky workaround to get some language feature into the Java language. jOOQ also has an annotation processor that helps validate SQL syntax for: Plain SQL usage (SQL injection risk) SQL dialect support (prevent using an Oracle only feature on MySQL) You can read about it more in detail … Continue reading How to Unit Test Your Annotation Processor using jOOR
Reporting a bug takes time, and trust me, every vendor appreciates your reporting of a bug! Your voice counts as many voices, for all the other customers of a product who do not want to or cannot take the time to report the same bug are numerous. So, first off, thanks for taking that time … Continue reading How to Create a Good MCVE (Minimal Complete Verifiable Example)
I like weird, yet concise language constructs and API usages https://twitter.com/nipafx/status/1055451667079008256 Yes. I am guilty. Evil? Don't know. But guilty. I heavily use and abuse the java.lang.Boolean type to implement three valued logic in Java: Boolean.TRUE means true (duh) Boolean.FALSE means false null can mean anything like "unknown" or "uninitialised", etc. I know - a … Continue reading Imperative Loop or Functional Stream Pipeline? Beware of the Performance Impact!
Clock's ticking. JDK 11 will remove a bunch of deprecated modules through JEP 320, which includes the Java EE modules, which again includes JAXB, a dependency of many libraries, including jOOQ. Thus far, few people have upgraded to Java 9 or 10, as these aren't LTS releases. Unlike in the old days, however, people will … Continue reading How to Patch Your IDE to Fix an Urgent Bug