Source code for vector addition has been sent to your email address.
Another 3 applets were created with EJS . The EJS source code are all available when you view those web page (just below the simulation if you login to this forum). If you want to check the java code , you can run EJS and open ejs source code, Click RUN to compile it  and you will find generated java code. EJS have many pre-build library for scientific simulation. I do not need to write code line by line. I just need to define variables, provide equation / differential equations and create graphic user interface with mouse drag an drop (then set up properties --related to variables) and EJS will generate java code and compile it. If you are interested in EJS please check out related forum at this web site  or visit EJS official web site.