Using command prompt and javac in Windows

If you want to compile your java programs from the command prompt instead of eclipse then follow the instructions below starting at the "Updating the PATH environment variable" section. I'm assuming that you already have JDK installed.

http://docs.oracle.com/javase/8/docs/technotes/guides/install/windows_jdk_install.html 

This is a simple guide to using command prompt to compile and run programs

http://www.cs.princeton.edu/courses/archive/spr05/cos126/cmd-prompt.html