Selenium Java - How to outsource @Config and call tests from an extern class?

I'm sure, this question can be answered very quickly by a experienced Java-developer. But as I am not that familiar with Java I don't get how to source out the @Config part of Selenium in Java. It would be optimal, if I could have a config-file or -class where I can put the data (browser, website etc.) on the one hand and on the other hand the test-files.
Here is an example of a test file:

package com.example_test.selenium;

import io.ddavison.conductor.Browser;
import io.ddavison.conductor.Config;
import io.ddavison.conductor.Locomotive;
import org.junit.Test;

@Config(
        browser = Browser.CHROME,
        url     = "http://example.com"
)

public class test_a_Home extends Locomotive {
    @Test
    public void testifExists() {
        validatePresent(site_a_Home.EL_NEWCUSTOMERBANNER);
    }
}

Now I would like to have a seperate file called tests.java where I can call the "test_a_Home"-function. If I try it just with

package com.example_test.selenium;

public class tests {
    test_a_Home test = new test_a_Home();

    test.testifExists();

}

I am receiving the error, that "testifExists()" cannot be resolved.
I tried changing the public void testifExists() to public int testifExists() and tried to call it with int res = test.testifExists(); in the class tests but this does not work either, as I receive the error java.lang.Exception: Method testNewCustomersBannerExists() should be void.
I would be very happy, if anyone could help me. If you need more information please feel free to mention it. Thank you.

Solution

If you want your design to be like this, then you need to organize your tests as such:

public class BasePage {
    public Locomotive test;
    public BasePage(Locomotive baseTest) {
        test = baseTest;
    }
}

public class test_a_Home extends BasePage {
    public test_a_Home(Locomotive baseTest) {
        super(baseTest);
    }

    public void testifExists() {
        test.validatePresent(site_a_Home.EL_NEWCUSTOMERBANNER);
    }
}

Then your test class, i'd recommend creating a base class as well:

@Config(
    browser = Browser.CHROME,
    url     = "http://example.com"
)
public class BaseTest extends Locomotive {}

And then your test class:

public class tests extends BaseTest {
    test_a_Home test = new test_a_Home(this);

    @Test
    public void testHomePage() {
        test.testIfExists();
    }
}

Also you state state:

I don't get how to source out the @Config part of Selenium in Java.

Please make sure you know, that using Conductor abstracts you from the Selenium API.. It just wraps it. @Config does not belong to Selenium, it belongs to Conductor.