To make better Apps, I want to understand the basics of Java. I understand the prinicples of inheritance, classes, can implement compilable code etc, but I don't understand the syntax and the structure of Java and how to make it myself. Especially, I want to learn how Java works in combination with Mendix. Can anyone recommend a (Dutch?) course? It might take a few days. Thanks.
There's no specific Java course in combination with Mendix, learning the specific Mendix API isn't hard once you already know some Java. I don't know about a Dutch course, but starting with the basics at the official tutorial (https://docs.oracle.com/javase/tutorial/java/index.html) isn't a bad idea, it's a pretty decent one.
When you have a real scenario to work on, you will learn much faster just by experience and having to solve real problems.
Sebastiaan van den Broek
There are some good books on the subject: top 9 books java
And lynda.com is always a good source for the basics.
In the Netherlands you can even do online courses with the LOI.