What is the name of the method that threads can use to pause their execution until signalled to continue by another thread？ （） Fill in the name of the method （do not include a parameter list）.

10. public class SuperCaic { 11. protected static int multiply（int a， int b） { return a * b； } 12. } and： 20. public class SubCalc extends SuperCalc { 21. public static int multiply（int a， int b） { 22. int c = super.multiply（a， b）； 23. return c； 24. } 25. } and： 30. SubCalc sc = new SubCalc（）； 31. System.out.println（sc.multiply（3，4））； 32. System.out.println（SubCalc.multiply（2，2））； What is the result？（）

A. 12 4
B. The code runs with no output.
C. An exception is thrown at runtime.
D. Compilation fails because of an error in line 21.
E. Compilation fails because of an error in line 22.
F. Compilation fails because of an error in line 31.

Given the following code， which statements concerning the objects referenced through the member variables i， j and k are true， given that any thread may call the methods a， b and c at any time？ （） class Counter { int v = 0； synchronized void inc（） { v++； } synchronized void dec（） { v--； } } public class Q7ed5 { Counter i； Counter j； Counter k； public synchronized void a（） { i.inc（）； System.out.println（"a"）； i.dec（）； } public synchronized void b（） { i.inc（）； j.inc（）； k.inc（）； System.out.println（"b"）； i.dec（）； j.dec（）； k.dec（）； } public void c（） { k.inc（）； System.out.println（"c"）； k.dec（）； } }

A. i.v is guaranteed always to be 0 or 1.
B. j.v is guaranteed always to be 0 or 1.
C. k.v is guaranteed always to be 0 or 1
D. j.v will always be greater than or equal to k.v at any give time.
E. k.v will always be greater than or equal to j.v at any give time.

Which are syntactically valid statement at// point x？（） class Person { private int a； public int change（int m）{ return m； } } public class Teacher extends Person { public int b； public static void main（String arg[]）{ Person p = new Person（）； Teacher t = new Teacher（）； int i； // point x } }

A. i = m；
B. i = b；
C. i = p.a；
D. i = p.change（30）；
E. i = t.b.

Which statements about inheritance are true？（）

A. In Java programming language only allows single inheritance.
B. In Java programming language allows a class to implement only one interface.
C. In Java programming language a class cannot extend a class and implement a interface together.
D. In Java programming language single inheritance makes code more reliable.

1. public class GoTest { 2. public static void main（String[] args） { 3. Sente a = new Sente（）； a.go（）； 4. Goban b = new Goban（）； b.go（）； 5. Stone c = new Stone（）； c.go（）； 6. } 7. } 8. 9. class Sente implements Go { 10. public void go（） { System.out.println（”go in Sente.”）； } 11. } 12. 13. class Goban extends Sente { 14. public void go（） { System.out.println（”go in Goban”）； } 15. } 16. 17. class Stone extends Goban implements Go { } 18. 19. interface Go { public void go（）； } What is the result？（）

A. go in Goban go in Sente go in Sente
B. go in Sente go in Sente go in Goban
C. go in Sente go in Goban go in Goban
D. go in Goban go in Goban go in Sente
E. Compilation fails because of an error in line 17.

1. interface TestA { String toString（）； } 2. public class Test { 3. public static void main（String[] args） { 4. System.out.println（new TestA（） { 5. public String toString（） { return “test”； } 6. } 7. } 8. } What is the result？（）

A. test
B. null
C. An exception is thrown at runtime.
D. Compilation fails because of an error in line 1.
E. Compilation fails because of an error in line 4.
F. Compilation fails because of an error in line 5.

10. class Nav{ 11. public enum Direction { NORTH， SOUTH， EAST， WEST } 12. } 13. public class Sprite{ 14. // insert code here 15. } Which code， inserted at line 14， allows the Sprite class to compile？（）

A. Direction d = NORTH；
B. Nav.Direction d = NORTH；
C. Direction d = Direction.NORTH；
D. Nav.Direction d = Nav.Direction.NORTH；

Which statement is true about assertion in the Java programming language？（）

Assertion expressions should not contain side effects.
B. Assertion expression values can be any primitive type.
C. Assertion should be used for enforcing preconditions on public methods.
D. An AssertionError thrown as a result of a failed assertion should always be handled by the enclosing method.

11. public interface Status { 12. /* insert code here */ int MY_VALUE = 10； 13. } Which three are valid on line 12？（）

A. final
B. static
C. native
D. public
E. private
F. abstract
G. protected