Venugobal makes a good choice in teaching data structures via the java interfaces. After all, as a java programmer, if you are learning some new java package, this is exactly how you probably learn it. A major point about the object oriented approach and encapsulation is to hide implementation details as lower level stuff.
So what happens in the book is that while learning about various data structures in the general sense, you can also quickly code and learn about using them. By availing yourself of those built into java. The standard java packages summarise a lot of effort by Sun in writing stable, highly debugged structures.
Of course, in a book like this, you do also need to understand implementations. A given data structure and algorithms that use it should not be a total black box. Hence, there are many details about sorting routines, queue implementations and tree traversals. There is a reasonable amount of rigour. Though the book is not at the level of Knuth's Art of Computer Programming, The, Volumes 1-3 Boxed Set (2nd Edition) (The Art of Computer Programming Series). Venugopal's exercises are a lot simpler than Knuth's.
However, if you are a java programmer, and you want to focus on what you are likely to most use, try looking into the hash table. In my java coding experience, the java Hashtable and HashSet are really common and useful entities. It turns out that they are also very easy to learn to use.