JAVA - Java Source Code File is a file that is written in simple programming language of Java. It uses a different type of approach now that it is owned by a different company. You can use the .CLASS files to bring out your entire most important source codes. It is important for you to make use of this file on your computer because many programs require you to have Java in order to open it up. It does come in handy for these purposes plus many more. Every major operating system can also take advantage of this file when they need to the most.