I know that if "you" have a good basic knowledge of languages, OOP, you can learn any language (if you have time and ... memory, sigh ).
Today there is no need to spend money to learn. You can find many sites that published tutorials, guides, source code examples and finally videos.
I never spent much time in Java (wrong, but when I can, I'll do it).
However, Java itself, is not very different from other languages such as VB.Net: apart from the syntax (if you need to change: "Dim A As Int" to "int A", it is not a big problem ), the important things are the usual ones: classes, interfaces, inheritance ...
The question is if you want to learn Java for Android or Java ever. Java is used almost anywhere and in many ways (Java beans? For soup? )
Anyway, you'll find a lot of free stuff on the Web.