public interface AbstractFormFactory {
    public Form createForm();
}

public interface Form {
    public void Show();
}

public class WindowsFormFactory implements AbstractFormFactory {
    public Form createForm() {
        return new WindowsForm();
    }
}

public class WindowsForm implements Form {
    public WindowsForm() {
        // algum código windows aqui
    }

    @Override
    public void Show() {
        // algum código windows aqui      
    }
}

public class MotifFormFactory implements AbstractFormFactory {
    public Form createForm() {
        return new MotifForm();
    }
}

public class MotifForm implements Form {
    public MotifForm() {
        // algum código motif aqui
    }

    @Override
    public void Show() {
        // algum código motif aqui
    }
}

public class Programa {
    public static void main(String[] args) {
        AbstractFormFactory fabricaEscolhida;
        if (args[1] == "Windows") {
            fabricaEscolhida = new WindowsFormFactory();
        }
        else  
        {
            fabricaEscolhida = new MotifFormFactory();
        }
        
        // criar janelas
        Form meuForm1 = fabricaEscolhida.createForm();
        Form meuForm2 = fabricaEscolhida.createForm();
        Form meuForm3 = fabricaEscolhida.createForm();
        Form meuForm4 = fabricaEscolhida.createForm();
    }
}