I have worked through a couple of common interview questions in Java here. Most of these have accompanying youtube videos.
Java: determine if a String has all unique characters
Java interview question: test for a pangram using char codes
Java interview question - test for Pangram using a HashSet
Java Next Permutation of a String Algorithm
Reverse an Integer in Java (Interview Questions)
Java Maps Part 3: use HashMap to find number of word occurrences in a file