Is there a projection matrix for the equirectangular projection

no

that's not something you change in the java code, it's something you set when you run the jar

read my full response

When programming in Java, you make other classes available to the class you are writing by putting something like this at the top of your source file:

import org.javaguy.coolframework.MyClass;

Or sometimes you 'bulk import' stuff by saying:

import org.javaguy.coolframework.*;

So later in your program when you say:

MyClass mine = new MyClass();

The Java Virtual Machine will know where to find your compiled class.

that's not classpath--that just references classes the program expects to be in the classpath

then how i set classpath

wait is the classpath like the main file like the main class like the compiled class file or whatever?

no it's a list of folders and jars containing classes the program being run can import

Download it from GitHub.