Java code to easily rotate a buffered image.
Continue reading “Rotate BufferedImage in Java”Rotate BufferedImage in Java
Simple method that correctly rotates a BufferedImage.
Computer Programming for Humanoids
Simple method that correctly rotates a BufferedImage.
Java code to easily rotate a buffered image.
Continue reading “Rotate BufferedImage in Java”Different results can both be correct. This depends on the grammar used to parse the expression. Some handle implied multiplication with higher precedence, others don’t.
There’s this meme on the internet about two calculators (or phone calculator apps) with different results. This is a common misconception and therefore a perfect topic for my blog.
Continue reading “It’s about RTFM, not BOMDAS!”I’ve once made a simple helper class for a set of bytes stored as an integer bitfield. So the idea is that each of the 32bits is used to represent if the ordinal number is in the set or not. This only works for the bytes 0 to 31.
Now this is an “inline class” – something we will get with Project Valhalla.
Here’s the branch of my project:
https://github.com/claudemartin/smallset/tree/valhalla
For this to work you need a JDK with a preview of Project Valhalla. Check java.net for that: http://jdk.java.net/valhalla/
Just download that JDK, clone my branch, build using Ant, and see what you can do with it. It’s actually a good example of an inline class, because it is just an integer (primitive) value but has methods (like a referenced type would). It doesn’t need object identity, but should still behave like an object. For example the sets are comparable. The type actually implements the Comparable
interface.
Note that this might not work with newer JDKs. I used JDK 14 + valhalla from java.net and the feature might look quite different in newer releases of Java.
I just saw that I never posted this here on my blog. JDBC is still a good way to just connect to some SQL database where JPA would be overkill. So I wrote a library that allows you to use the Java Stream API to process that data.
https://github.com/claudemartin/streamed-sql
Connection conn = dbpool.getConnection();
var strsql = StreamedSQL.create(conn, true);
try (Stream<Foo> stream = strsql.stream("SELECT * FROM FOO", Foo::new)) {
stream.filter(f -> f.getName().startsWith("L")).sorted().forEachOrdered(System.out::println);
}
LIFO queue that will drop old elements when needed.
Have a Last-In-First-Out queue (implements java.util.Queue<E>) that will release old elements so that garbage collection (GC) can remove them. Like a cache that is a stack.
Continue reading “WeakAssQueue”I think I’ve just found a mistake in the Java Tutorial.
Maybe I’m just being pedantic, but I think I’ve just found a mistake in the Java Tutorial. It claims:
All binary operators except for the assignment operators are evaluated from left to right; assignment operators are evaluated right to left.
The Java™ Tutorials » Language Basics » Operators
What is this supposed to mean? Evaluation from right to left would mean that when you have a line like the following you get the rightmost expression evaluated first:
int x = 42;
x += getNumber();
// The above would be equivalent to:
x = getNumber() + x;
But that’s not how Java actually evaluates this expression. And the JLS 12 (2019-02-08) clearly states in 15.26.2 that “the value of the left-hand operand is saved and then the right-hand operand is evaluated.”
Continue reading “Java Assignments are evaluated Left to Right”With Windows Subsystem for Linux (WSL) we can now use Linux tools, such as grep
, rsync
, ssh
, and network commands, such as dig
and netstat
, on Windows directly. No need for cygwin or other 3rd party software.
Here’s an example on how uname
is unknown to Windows, but WSL (Ubuntu in my case) knows it:
For beginners it is difficult to understand what a variable is. They are used in nearly all high-level languages and therefore vital for a good understanding of programming
Continue reading “What is a Variable?”Many misconceptions in Java and similar languages stem from the bad default behaviour. I’ll explain some of them.
Continue reading “Bad Defaults in Java”Java isn’t easy. It’s often more complex than needed. But being easy for beginners shouldn’t be a design goal with high priority.
Should a programming language be easy?
I don’t know why so many educational establishments use Java to teach programming. They often start with Java in the first semester. Even the Oracle tutorials expect the reader to already know some basics. Java was designed for programmers who already know C/C++ as seen in this example.
Continue reading “Is Java easy?”The
main
method is similar to themain
function in C and C++; it’s the entry point for your application and will subsequently invoke all the other methods required by your program. [Lesson: A Closer Look at the “Hello World!” Application]