Passing Variable From One Class To Another

I would like to setup a boolean called dFlag in the main.class of my program and reference it in another class.

I already have it setup to work locally just hitting a snag on how to do it.

Code:
public class Main extends Activity {
boolean dFlag; ///Debug flag, true=enabled | false=disabled
}
public class Other extends Activity {
if(dFLag = true) {
///Output debug message
}
}

Or is there an easier way to do what I want without having to re-invent the wheel so to speak?