While learning to code in Java, As Java is the most popular language nowadays and the CheatSheet will be very handy which explains you the basic concepts of Java. java is the most popular language when it comes to Web Apps.
This CheatSheet has been released by the Princeton University and its very needy at times. It includes the the basics like structure, input/output, data types, functions and a lot more… Checkout the link above and you will know it much better.
[Source: Java Programming Cheatsheet]