FontUtils | A Tiny Font Utility Library | User Interface library

NoClassDefFoundError means that you do not have that referenced dependency in your classpath. This is typically resolved by using a dependency manager like Maven or by copying the jar manually into your project root.

Specifically, in your question, you are missing the org.slf4j.LoggerFactory package at compile time.

Put return statement to your listener as true, not false and make sure you set it after you set your adapter!

EDIT:

As you cant select the rbuttons but your OnClick is fired let's add selection manually to the clicked button

FontRegistry manages all the Fonts that it owns and deals with disposing of them.

The JavaDoc says:

A font registry owns all of the font objects registered with it, and automatically disposes of them when the SWT Display that creates the fonts is disposed. Because of this, clients do not need to (indeed, must not attempt to) dispose of font objects themselves.

This is done using the disposeExec method of Display.

ImageRegistry is the same:

An image registry owns all of the image objects registered with it, and automatically disposes of them when the SWT Display that creates the images is disposed. Because of this, clients do not need to (indeed, must not attempt to) dispose of these images themselves.

ImageRegistry does also have a dispose method if you want to dispose of images earlier.

Note: It is possible to create an ImageRegistry using your own ResourceManager, in this case it is up to the resource manager to arrange disposal.

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