java

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

How to populate a Java int array with a range of values

I just learned an easy way to populate/initialize a Java int array with data, such as a range of numbers. The key is to use the rangeClosed method on the Java 8 IntStream class. Here’s an example using the Scala REPL:

scala> val n = java.util.stream.IntStream.rangeClosed(0, 10).toArray()
n: Array[Int] = Array(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10)

I show that in Scala to show the output, and here’s what it looks like with Java:

Java int, double, float, and mixed-type arithmetic rules

Table of Contents1 - The answer2 - More Java division and arithmetic rules3 - Summary

Java FAQ: What are the rules about Java arithmetic (multiplication, division) involving mixed data types?

While working on a math problem in Java just a little while ago, I realized that I wasn’t comfortable with the Java mixed-type division rules. That is, I wondered if the result of this equation:

3 / 2

the same as the result of this equation:

3 / 2.0

or this equation:

3.0 / 2.0

How to use multiple regex patterns with replaceAll (Java String class)

Table of Contents1 - 1) A simple string2 - 2) Replace multiple patterns in that string3 - 3) More explanation4 - Multiple search patterns5 - Summary

Java FAQ: How can I use multiple regular expression patterns with the replaceAll method in the Java String class?

Here’s a little example that shows how to replace many regular expression (regex) patterns with one replacement string in Scala and Java. I’ll show all of this code in Scala’s interactive interpreter environment, but in this case Scala is very similar to Java, so the initial solution can easily be converted to Java.

A Java method to replace all instances of a pattern in a String with a replacement pattern

Note: The code shown below is a bit old. If you want to perform a “search and replace” operation on all instances of a given pattern, all you have to do these days is use the replaceAll method on a Java String, like this:

String s = "123 Main Street";
String result = s.replaceAll("[0-9]", "-");

That second line of code returns the string “--- Main Street”. I kept the information below here for background information.

How to determine the current monitor size with multiple displays - Java Swing, JavaFX

Note: This code is currently a work in progress. I know of possible approaches, but I don’t know of a perfect working solution yet.

I’m currently trying to find the right way to find the current monitor size, when you’re writing a Java Swing application to work in a multiple-monitor configuration. I always use three monitors, so I can test this pretty easily.

A Java TimerTask, Timer, and scheduleAtFixedRate example

As a quick note, if you ever need to use a Java TimerTask, you can define one like this:

class BrightnessTimerTask extends TimerTask {
    @Override
    public void run() {
        // your custom code here ...
    }        
}

and you can then instantiate it, create a Timer, and schedule the task like this: