多选题 Given:
1. public class Glank implements Vonk {Jooker[] j; }
2. abstract class Bostron {String yoodle; Bostron b;
3. interface Protefor { }
4. interface Vonk extends Protefor {int x = 7; }
5. class Jooker {Bostron b; }
Which are true? (Choose all that apply.)