java

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

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’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:

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.