How do I run test code in different file under a project

[lostbit]

New to Java and eclipse, not sure if my question is java or eclipse question so I will try post on both forums.
Lets say you have a project, class, file created and the code you wrote so far works. In my case I wanted to
add getting system time and using some math. Found examples on the net none worked. My next step is to
try the inter net code examples in a separate file by it's self. So I tried adding another file, past the code there
then try to run it and only the first file runs. SO I guess my question is this, must I create a new project, class,
file to test a code section in this fashion?

[KevinWorkman]

What happens when you compile and run from the command line? Post an SSCCE demonstrating what you're trying to do, as well as the exact output from the command line, an we'll go from there.