boolean init on demand.

gistfile1.txt

public class FooBar {

    static Boolean tmpVal;

    public static void main(String[] args) {
        tmpVal = true; // readFromConfig

        // Assuming config is initialized before method is called
        foo();
    }

    public static void foo() {
        if (Instance.val) {
            // foo
        } else {
            // bar
        }
    }

    private static class Instance {
        static final boolean val;
        static {
            val = requireNonNull(FooBar.tmpVal, "tmpVal must be initialized before first test");
        }
    }
}