How to update the Java keystore with a website certificate (Let’s Encrypt) alvin June 17, 2018 - 5:51pm

As a brief note to self, I use these Java keytool commands to add/update the SSL certificate for accessing a website named

A printf format reference page (cheat sheet)

Summary: This page is a printf formatting cheat sheet. I originally created this cheat sheet for my own purposes, and then thought I would share it here.

A cool thing about the printf formatting syntax is that the specifiers you can use are very similar, if not identical, between several different languages, including C, C++, Java, Perl, Ruby, and others, so your knowledge is reusable, which is a good thing.

Java 10: How to implement About, Preferences, and Quit menu items on MacOS alvin June 2, 2018 - 5:20pm

If you want to implement About, Preferences, and Quit handlers with Java 9 and newer on MacOS systems, this example Java source code shows how to do it:

Oracle plans to drop support for data serialization/deserialization from Java alvin May 31, 2018 - 10:28am

“Oracle plans to drop support for data serialization/deserialization from the main body of the Java language, according to Mark Reinhold, chief architect of the Java platform group at Oracle.”

~ A quote from a story that is covered well on this site, and it looks like the original article is at InfoWorld.

A Java Factory Pattern example

Java Design Patterns FAQ: Can you provide an example of the Factory Pattern in Java?

Sure. In this article we'll look at a small-but-complete example of the Factory Pattern ("Factory Design Pattern") implemented in Java.

How to convert a Java Map to a Scala Map using JavaConverters

Here’s a quick look at how to convert a Java Map (such as HashMap) to a Scala Map using the JavaConverters object:

// import what you need
import java.util._
import scala.collection.JavaConverters._

// create and populate a java map
val jMap = new HashMap[String, String]()
jMap.put("first_name", "Alvin")
jMap.put("last_name",  "Alexander")

// convert the java map to a scala map
val sMap = jMap.asScala

How to use the Lightbend Config library in a Scala or Java application

Table of Contents1 - Adding the Lightbend Config dependency2 - A Scala application that uses Lightbend Config3 - The Lightbend Config configuration file4 - Discussion

If you want to use Lightbend Config configuration files in your Scala or Java application, here’s a quick example of how to configure and use Lightbend Config in your application. In this case I’m specifically using Scala and SBT.

How to speed up JDBC PreparedStatement MySQL batch inserts

If you ever need to batch-insert a lot of records into a MySQL/MariaDB database using the JDBC PreparedStatement (as in preparedStatement.executeBatch()) be sure to change the MySQL URL to use the rewriteBatchedStatements, as shown here:


For a recent project I needed to batch-insert about eleven million records into a MySQL database, and the runtime was about 55 minutes. Once I added rewriteBatchedStatements=true to the MySQL URL, the batch-insert time was reduced down to only three minutes. That one little change made all the difference.