现有: 1. class Top { 2 . static int x=l; 3. public Top (int y) { x*=3; } 4. } 5. 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); 1O. } 11. } 结果为( )