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Visual studio code cannot find java libraries

I've setup a Java project in Visual Studio Code. I installed previously a few java extensions :
and I can create a program that does Hello World.
In a folder called lib inside the project folder, I copied some jars (lwjgl3) and, although are shown by intellisense when I try to import them, I have an error that says it cannot find the package :
Anything I missed ?

You need to add the jar to your classpath. The classpath is something used by java to find the libraries your program uses. Java looks in each folder/jar archive to find the class files, because it would be slow if it searched every directory on your computer. See this question: What is a classpath and how do I set it?

Add a reference to the package in the following way.
Click the plus sign to the right of Referenced Libraries under the JAVA PROJECTS panel
Select the .jar file in the pop-up window.

JavaFX Eclipse suggestion to import not present

I am just starting with JavaFX and for some reason, Eclipse does not suggest to import JavaFX stuff so I have to type it in manually. Example: javafx.scene.Group I typed in Group as a type and it suggested other things such as javax.swing.GroupLayout.Group
image of suggestions
I'm not exactly sure, but I think maybe the fact that the JavaFX library is under Modulepath instead of Classpath has to do with it, but it only works if it is under Modulepath.
Help would be greatly appreciated, thanks!

I'm rewriting this answer, as #kleopatra pointed out it was inexact
For suggestions to work, you need to have JavaFX on your project's build path.
If you've created a plain Java project in Eclipse, with a module-info.java at it's source path root, then you need to add all the required jars to the module path:
JavaFX SDK should already be installed on your system, or download it from Gluon and unzip it
Right-click your Java project, got to Build Path -> Configure Build Path...
Go to Libraries tab, point to the Modulepath section
Click [Add External JARs...] button, pick all the jars from JavaFX SDK, hit [Apply and close]
Then suggestions should work as expected, and imports will be automatically inserted at the top of your java files, but they will appear in error the first time you import anything from a given library module, as this module must also be required in your module-info.java. You can do that automatically with a quick fix ("Add 'requires javafx.something' to module-info.java") when hovering the import.
Now there's a more straightforward way to create a JavaFX modular project in Eclipse, using Maven:
Create a new Maven Project
Check and pass the first wizard screen
Select archetype org.openjfx:javafx-archetype-fxml
On the next screen, you can select the JavaFX version of your choice (currently 13 by default)
After the wizard terminates, you've got a nice little project already setup with an application window and two FXML sample displays. You can start from there to build your own project.

Eclipse Not Finding Classes added to the build Path (Java Dynamic Web Project)

I am taking over a web project from my school. I am trying to deploy the project in eclipse. The project uses a group of libraries (Namely javax.mail.* , com.sun.mail.*, org.joda.* and org.apache.*). The project can not compile because it is unable to locate these. I have them in the src folder and then added the three top level folders/packages to the build path. The import statements work. But getting the joda.time.CLASSXYZ does not work (Then I instantiate the class CLASSXYZ). (The error is "The type org.joda.time.base.BaseDateTime cannot be resolved. It is indirectly referenced from required .class files" the import was joda.time.* so the class should have been imported)
I've looked at the other threads and most of them just explain how to add folders to the build path. I have Apache tomcat set up with eclipse. It works with other projects that I have deployed.
This problem has gotten pretty frustrating as its preventing me from starting the project. Any help you be much appreciated.
Cheers

Unless you use maven you need to download additional libraries:
javax.mail: http://www.oracle.com/technetwork/java/javamail/index.html (also included in Java EE)
org.apache http://commons.apache.org/
org.joda http://joda-time.sourceforge.net/
I suggest to place them in a folder 'lib' and add the jar-files to your build class path. (context menu on your project).

The other threads you mentioned are pointing you in the right direction, and provide a good practice to get in to (especially once you start having more than one project running in your eclipse ide).
So right click project - Build Path - Configure Build Path... , then in the Libraries tab, click Add External JARs and add in the jar for org.joda from the link in the other answer here. This way you can have all your external jar libraries in one spot and reuse them across multiple projects. There's also about a dozen different ways to do the same thing in eclipse, but this is the most direct I think. I'm on version Helios (your's might be slightly different). I try not to use source files of external code libraries unless I want to play around, debugging their code - not a bad thing to do - but I never have the time to spare for that.
Also I'd double check that the other libraries you mentioned aren't being automatically linked in or included as part of the JRE system library. Especially if you are setup in a Dynamic Web Project, it would surprise me if org.apache wasn't already there... but I could easily be wrong there, have been many times before & eclipse was usually involved ;-)

How to install jar library?

I've downloaded the ANTLR Java runtime libraries. It's a jar file. It contains "org.antlr.runtime". Where do I put it so that the Java compiler can find it? Do I need to extract it? I'm using NetBeans (for now), if relevant.

Assuming you can find your jdk folder, You can move the .jar file into the jdk\jre\lib\ext folder, where other .jar files are placed. After doing so, NetBeans should be able to run files with access to the library

For NetBeans you go to your Projects Tab and then right-click on the project you want the library added to then click Properties. Go to the Libraries bullet then on the right side click on Add JAR/Folder. No need to extract it. All you have to do is right click in the editor window and click Fix Imports.
For use outside of NetBeans you have to add it to your Java classpath.

For java command line you need to add it to your class path however in Netbeans you just need to add it as a library. It can be anywhere. Google to find out how to do these things.
In fact in netbeans, you can just say you need this in your maven project and it will do the download of the jar and its source/documentation as required.

In java, how do you import one project into another without having them in the same (Eclipse) workspace?

I've been a c++ programmer for 10 years, i'm used to just creating libraries and then linking to them from my existing project. However in java, i have 2 projects, one is my game engine, the other is the test environment that i would like to use, here is how it is structured:
com.logic.engine
com.logic.testapp
yet in my test app, i cannot do
import com.logic.engine.*;
it simply cannot find the reference.
How can I do this without having to copy and paste my engine into every program i write with it?

Package your engine as a jar, and add the jar to the classpath of the projects that use it.

In eclipse you can also declare that your test prgram depends on your game engine. The classes will then be available. Check in the build paths dialog available from the context menu in the project view.

In eclipse, right click on your test project in the Project Explorer and select Properties. In the "Java Build Path" section, go to the Projects tab and add your engine project.

You need to change the classpath to include the folder containing your engine.
java -cp /path/to/engine testapp

I just fired up Eclipse to check this out.
You should see a red wavy underline on import com.logic.engine.*; - mouse over this and it'll tell you that the import could not be resolved and offer you a number of so-called quick fixes. One of those should be Fix Project Setup - that will offer to fix things for you, in this case to add one project to the other's build path.