Use this book at your own peril.
I have 2nd ed of data structures Made easy in Java & it has lots of errors.
I am currently revising Binary tress chapter & below are some of the errors in the book :
1)AVL tree is explained wrong -RR rotation diagram is actually shown as diagram of LL rotation & vice versa .Even the resultant diagram after rotation is wrong as it contains duplicate digits(8 & 8) in place of correct digits(5 & 8)as in diagram before rotation.
I wasted 1 day to learn AVL ,wrongly, from this book & took 1 day to learn it correctly from these source-https://courses.cs.washington.ed... and
http://cise.ufl.edu/~nemo/co...
2) AVL diagram in the book is not even BST.
3)Binary tress : some of the problems like Kth smallest element in BST is explained by taking variable “count” as method parameter . The count should either be a global variable or static variable for the code to work.I think the code was copied from c++ & changed it to Java without even running/verifying the code.
There are many such errors for binary tress in the book.And i am just mentioning the errors in a single chapter.
The reason i still refer this book is because even after so many errors,it’s still a good reference material for DS in java.Topics that are explained quite well in this book-Graph ,LinkedList,Hashing,Searching.
The book is full of errors & my advise is to try GeeksForGeeks or try some other standard book like Robert Lafore’s, Cormen etc with this book.