CodingBat is a free site of live coding problems to build coding skill in Java and Python. Going through many practice problem is a great way to solidify your understanding of how the code should work. The CodingBat problems are designed to have low overhead: short problem statements (like an exam), nothing to install, immediate feedback in the browser, and there's lots of them to build up those skills.You can practice here and improve your skills at the same time.