I know C and C++ and I have some experience with Java, but I don't know too much about Algorithms and Data Structures.
I did a search on Amazon, but I don't know what book should I choose. I don't want a book which put its basis only on the theoretic part; I want the practical part too (probably more than the theoretical one :) ).
I don't want the code to be implemented in a certain language, but if is in Java, probably I would happier. :)
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algorithm
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The answer is
Introduction to Algorithms by Cormen et. al. is a standard introductory algorithms book, and is used by many universities, including my own. It has pretty good coverage and is very approachable.
And anything by Robert Sedgewick is good too.
If you want the algorithms to be implemented specifically in Java then there is Mitchell Waite's Series book "Data Structures & Algorithms in Java". It starts from basic data structures like linked lists, stacks and queues, and the basic algorithms for sorting and searching. Working your way through it you will eventually get to Tree data structures, Red-Black trees, 2-3 trees and Graphs.
All-in-all its not an extremely theoretical book, but if you just want an introduction in a language you are familiar with then its a good book. At the end of the day, if you want a deeper understanding of algorithms you're going to have to learn some of the more theoretical concepts, and read one of the classics, like Cormen/Leiserson/Rivest/Stein's Introduction to Algorithms.
I think introduction to Algorithms is the reference books, and a must have for any serious programmer.
http://en.wikipedia.org/wiki/Introduction_to_Algorithms
Other fun book is The algorithm design manual http://www.algorist.com/. It covers more sophisticated algorithms.
I can't not mention The art of computer programming of Knuth http://www-cs-faculty.stanford.edu/~knuth/taocp.html
If you don't need in a complete reference to the most part of algorithms and data structures that are in use and just want to get acquainted with common techniques I would recommend something more lightweight than Cormen, Sedgewick or Knuth. I think, Algorithms and Data Structures by N. Wirth is not as bad choice even in spite of it was printed far ago.
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