java

recent posts related to java, jdbc, spring, etc.

How to convert a Java array into a Stream

If you ever need to convert a Java array into a Stream, there are at least two ways to do it.

1) Converting an array to a Stream

First, to convert the entire array to a Stream, use the Stream.of static method like this:

Some RxJava example source code (Hackers at Cambridge tutorials)

I recently watched the three Hackers at Cambridge Introduction to RxJava videos, and coded along with them. If you’re interested in some example RxJava code, here’s what I typed in.

The first thing you do is create a new Gradle/Java project with these commands:

mkdir MyProject
cd MyProject
gradle init --type java-application

With that project created you can begin creating some Java/RxJava code.

Some Java file utilities

As a bit of warning, this is some old Java code, but if you want to create your own Java file utilities (utility methods), this code might help you get started:

An example of JSoup’s OutputSettings class

I ended up not using this code, but if you wanted to see one way to use JSoup’s OutputSettings (Document.OutputSettings) class to set some parameters before calling JSoup.clean, I hope this is helpful:

// tried some things to improve the html output
val settings: OutputSettings = new OutputSettings
settings.prettyPrint(true)  //`true` is default
settings.charset("UTF-8")
settings.outline(true)  //this is close to what i want, but too extreme
settings.indentAmount(4)
val cleanHtml: String = Jsoup.clean(html, "", wl, settings)

I can attest that this code works, it’s just not what I need at the moment.

Also, the code shown is written in Scala, but as you can see, it converts easily to Java.

How large can a Java BigInteger be?

Java FAQ: How large can a Java BigInteger be?

Answer: The Java BigInteger Scaladoc states the following:

“BigInteger must support values in the range -2Integer.MAX_VALUE (exclusive) to +2Integer.MAX_VALUE (exclusive) and may support values outside of that range.”

The Scala BigInt wraps Java’s BigInteger, so it will also have the same data range.

Java 9 and 10 saw virtually no deployment to production alvin January 3, 2019 - 9:31am

In this InfoQ Java in 2019 Predictions article, this line stood out the most: Java 9 and 10 saw virtually no deployment to production. Working alone I occasionally wonder what large companies are doing, and with these Java major version number releases coming every six months I was wondering how that was playing out.

Java’s javap command doesn’t show private members (by default)

As I was just reminded, Java’s javap command doesn’t show private members by default. You have to use the -p option of javap to see private members.

I was just reminded of that when using the Scala REPL. Given this Person class with a private constructor field named name:

class Person(private var name: String)

javap without the -p option shows this:

Java example: JMenuBar + KeyStroke + AbstractAction

As a brief note, here’s some source code that I used to create a JMenuBar in a Java application. First, I defined some fields in my main class:

private static final KeyStroke fileOpenKeystroke = KeyStroke.getKeyStroke(KeyEvent.VK_O, Event.META_MASK);
private Action fileOpenAction;
private JMenuBar menuBar;

Later in the same class I defined this method: