Generate UML Class Diagram from Java Project

I´d say MoDisco is by far the most powerful one (though probably not the easiest one to work with).

MoDisco is a generic reverse engineering framework (so that you can customize your reverse engineering project, with MoDisco you can even reverse engineer the behaviour of the java methods, not only the structure and signatures) but also includes some predefined features like the generation of class diagrams out of Java code that you need.

How about the Omondo Plugin for Eclipse. I have used it and I find it to be quite useful. Although if you are generating diagrams for large sources, you might have to start Eclipse with more memory.

I wrote Class Visualizer, which does it. It's free tool which has all the mentioned functionality - I personally use it for the same purposes, as described in this post. For each browsed class it shows 2 instantly generated class diagrams: class relations and class UML view. Class relations diagram allows to traverse through the whole structure. It has full support for annotations and generics plus special support for JPA entities. Works very well with big projects (thousands of classes).

I use eUML2 plugin from Soyatec, under Eclipse and it works fine for the generation of UML giving the source code. This tool is useful up to Eclipse 4.4.x