单选题 现有: 1. class Top { 2. static int x = 1; 3. public Top(int y) { x *= 3; } 4. } 5. public class Middle extends Top { 6. public Middle() { x += 1; } 7. public static void main(String[] args) { 8. Middle m = new Middle(); 9. System.out.println(x); 10. } 11. } 结果为