Java Programming: Final Examination 6/ 姓名 : 學號 : 分數 :

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1 Java Programming: Final Examination 6/ 姓名 : 學號 : 分數 : I (105 pts) 選擇題 [Questions marked with * (ex: Question 9) mean they have more than one answer ] 1. Fill in the blank in: Comparable c = new Date(); so that c.compareto( new Date()) executes normally. a) <?> b) <E> c) <String> d) <Date> 2. If you want to store non-duplicated objects in the order in which they are inserted, you should use. a) LinkedHashSet b) ArrayList c) HashSet d) LinkedList e) TreeSet 3. Which method do you use to test if an element e is in a set or list named x? a) x.include(e) b) (e instanceof List) (e instanceof Set) c) x.in(e) d) x.contain(e) e) x.contains(e) 4. Which of the following is correct to perform the set intersection of two sets s1 and s2? a) s1.intersect(s2) b) s1.intersection(s2) c) s1.join(s2) d) s1.retainall(s2) 5. The printout of the following code is. LinkedHashSet<String> set1 = new LinkedHashSet<String>(); set1.add("new York"); LinkedHashSet<String> set2 = (LinkedHashSet<String>)(set1.clone()); set1.add("atlanta"); set2.add("dallas"); System.out.println(set2); a) [New York, Atlanta, Dallas] b) [New York, Dallas] c) [New York] d) [New York, Atlanta] 6. Suppose set s1 is [1, 2, 5] and list L2 is [2, 3, 6]. After s1.addall(l2), s1 is. a) [1, 2, 2, 3, 5, 6] b) [2] c) [1, 5] d) [1, 2, 3, 5, 6] e) runtime exception 7. Suppose set s1 is [1, 2, 5] and set s2 is [2, 3, 6]. After s1.removeall(s2), s1 is. a) [1, 5] b) [1, 2, 2, 3, 5, 6] c) [1, 2, 3, 5, 6] d) [2] 8. The method in the Queue interface retrieves and removes the head of this queue, or null if this queue is empty. a) remove() b) poll() c) element() d) peek() 9. * To create a set that consists of string elements "red", "green", and "blue", use a) new HashSet(new String[ ]{"red", "green", "blue"}) b) new LinkedHashSet(Arrays.asList(new String[ ]{"red", "green", "blue"})) c) new Set(Arrays.asList(new String[ ]{"red", "green", "blue"})) d) new HashSet(Arrays.asList(new String[ ]{"red", "green", "blue"})) e) new HashSet({"red", "green", "blue"}) 10. Which of the following is correct to create a list from an array? a) new ArrayList(new String[ ]{"red", "green", "blue"}) b) new List({"red", "green", "blue"}) c) new LinkedList(new String[ ]{"red", "green", "blue"}) 1

2 d) Arrays.asList(new String[ ]{"red", "green", "blue"}) e) new List(new String[ ]{"red", "green", "blue"}) 11. Which of the following is correct to sort the elements in a list lst? a) lst.sort() b) Collections.sort(lst) c) new LinkedList(new String[ ]{"red", "green", "blue"}) d) Arrays.sort(lst) 12. To get an iterator from a set, you may use the method. a) iterators b) finditerator c) getiterator d) iterator 13. Which of the data types below could be used to store elements in their natural order based on the compareto method. a) Collection b) HashSet c) Set d) TreeSet e) LinkedHashSet 14. Which of the following data types does not implement the Collection interface? a) HashSet b) ArrayList c) Map d) TreeSet e) LinkedList 15. Which of the data types below does not allow duplicates? a) List b) LinkedList c) Stack d) Vector e) Set 16. Which of the following statements is not defined in the Object class? a) sleep(long milliseconds) b) tostring() c) notifyall() d) wait() e) notify() 17. * You can use the method to temporarily release time for other threads. a) suspend() b) stop() c) yield() d) sleep(long milliseconds) 18. Which of the following expressions must be true if you create a thread using Thread = new Thread(object)? a) object instanceof Runnable b) object instanceof Thread c) object instanceof String d) object instanceof Number 19. Analyze the following code: public abstract class Test implements Runnable { public void dosomething() { }; } a) The program will not compile because it does not contain abstract methods. b) The program will not compile because it does not implement the run() method. c) The program compiles fine. d) None of the above. 20. *Which of the following methods are in the Collection interface? a) isempty() b) clear() c) size() d) getsize() 21. *The Collection interface is the base interface for. a) Map b) List c) Set d) LinkedList e) ArrayList 22. When you run the following program, what will happen? public class Test extends Thread { public static void main(string[ ] args) { Test t = new Test(); t.start(); t.start(); } public void run() { System.out.println("test"); } a) The program displays test twice. b) Nothing is displayed. 2

3 c) The program displays test once. d) An illegal java.lang.illegalthreadstateexception may be thrown because you just started thread t and thread might have not yet finished before you start it again. t cannot be restarted! 23. You can use the method to force one thread to wait for another thread to finish. a) sleep(long milliseconds) b) yield() c) suspend() d) join() e) stop() 24. Which of the following declarations use raw type? a) ArrayList<String> list = new ArrayList<String>(); b) ArrayList<Object> list = new ArrayList<Object>(); c) ArrayList list = new ArrayList(); d) ArrayList<Integer> list = new ArrayList<Integer>(); 25. To create a list to store integers, use a) ArrayList<Object> list = new ArrayList<Integer>(); b) ArrayList<Number> list = new ArrayList<Integer>(); c) ArrayList<Integer> list = new ArrayList<Integer>(); d) ArrayList<int> list = new ArrayList<int>(); 26. To declare a class named A with a generic type, use a) public class A(E) {... } b) public class A(E, F) {... } c) public class A<E, F> {... } d) public class A<E> {... } 27. Which of the following methods in Thread throws InterruptedException? a) setpriority(int) b) sleep(long) c) yield() d) run() e) start() 28. Suppose there are three Runnable tasks, task1, task2, task3. How do you run them in a thread pool with 2 fixed threads? a) ExecutorService executor = Executors.newFixedThreadPool(2); executor.execute(task1); executor.execute(task2); executor.execute(task3); b) new Thread(task1).start(); new Thread(task2).start(); new Thread(task3).start(); c) ExecutorService executor = Executors.newFixedThreadPool(1); executor.execute(task1); executor.execute(task2); executor.execute(task3); d) ExecutorService executor = Executors.newFixedThreadPool(3); executor.execute(task1); executor.execute(task2); executor.execute(task3); 29. Which of the following method is a static in java.lang.thread? a) join() b) setpriority(int) c) sleep(long) d) run() ) start() 30. The equals method is defined in the Object class. Which of the following is correct to override it in the String class? a) public boolean equals(string other) b) public static boolean equals(object other) c) public static boolean equals(string other) d) public boolean equals(object other) 31. Which of the statements regarding the super keyword is incorrect? a) You can use super to invoke a super class constructor. b) You cannot invoke a method in superclass's parent class which is overridden by a superclass method. c) You can use super.super.p to invoke a method in superclass's parent class. d) You can use super to invoke a super class method. 32. You can assign to a variable of Object[ ] type. 3

4 a) new String[100] b) new int[100] c) new double[100] d) new char[100] 33. Suppose A is an inner class in Test. A is compiled into a file named. a) A.class b) A$Test.class c) Test$A.class d) Test&A.class 34. Which statement is true about a non-static inner class? a) It must be final if it is declared in a method scope. b) It can access private instance variables in the enclosing object. c) It can only be instantiated in the enclosing class. d) It is accessible from any other class. e) It must implement an interface. 35. *Which of the following statements is correct? a) Comparable<String> c = new Date(); b) Comparable<Object> c = new Date(); c) Comparable<String> c = new String("abc"); d) Comparable<String> c = "abc"; 36. A variable defined inside a method is referred to as. a) a method variable b) a local variable c) a block variable d) a global variable 37. All Java applications must have a method. a) public static main(string[ ] args) b) public static Main(String args[ ]) c) public static void main(string[ ] args) d) public void main(string[ ] args) 38. Suppose your method does not return any value, which of the following keywords can be used as a return type? a) void b) double c) public d) int e) None of the above 39. Which of the following statements are correct? a) char[ ][ ][ ] chararray = new char[2][2][ ]; b) char[ ][ ][ ] chararray = new char[][2][2]; c) char[ ][ ][ ] chararray = {{'a', 'b'}, {'c', 'd'}, {'e', 'f'}}; d) char[2][2][ ] chararray = {'a', 'b'}; 40. Which of the following statements are correct? a) char[2][2] chararray = {{'a', 'b'}, {'c', 'd'}}; b) char[ ][ ] chararray = {'a', 'b'}; c) char[ ][ ] chararray = {{'a', 'b'}, {'c', 'd'}}; d) char[2][ ] chararray = {{'a', 'b'}, {'c', 'd'}}; 41. Which of the following declarations are correct? a) public static void print(string... strings, double... numbers) b) public static void print(double... numbers, String name) c) public static void print(int n, double... numbers) d) public static double... print(double d1, double d2) 42. Which of the following kind of nested classes can be instantiated without the need of a containing object? a) Anonymous inner class. b) Local class. c) Member inner class d) Static nested class. 43. The method copies the sourcearray to the targetarray. a) System.arrayCopy(sourceArray, 0, targetarray, 0, sourcearray.length); b) System.copyArrays(sourceArray, 0, targetarray, 0, sourcearray.length); c) System.arraycopy(sourceArray, 0, targetarray, 0, sourcearray.length); d) System.copyarrays(sourceArray, 0, targetarray, 0, sourcearray.length); 44. Assume int[ ] t = {1, 2, 3, 4}. What is t.length? 4

5 a) 5 b) 0 c) 4 d) *Which of the following statements is valid? a) int i = new int(30); b) char[ ] c = new char(); c) double d[ ] = new double[30]; d) int[ ] i = {3, 4, 3, 2}; e) char[ ] c = new char[4]{'a', 'b', 'c', 'd'}; 46. If you declare an array double[ ] list = {3.4, 2.0, 3.5, 5.5}, the highest index in array list is. a) 3 b) 4 c) 0 d) 1 e) What is the representation of the third element in an array called a? a) a[3] b) a(3) c) a(2) d) a[2] 48. You can declare two variables with the same name in. a) two nested blocks in a method (two nested blocks means one being inside the other) b) a block c) different methods in a class d) a method one as a formal parameter and the other as a local variable 49. To prevent a class from being instantiated, a) use the static modifier on the constructor. b) don't use any modifiers on the constructor. c) use the private modifier on the constructor. d) use the public modifier on the constructor. 50. A method that is associated with an individual object is called. a) a static method b) an instance method c) a class method d) an object method 51. Variables that are shared by every instances of a class are. a) class variables b) public variables c) instance variables d) private variables 52. The default value for data field of a boolean type, numeric type, object type is, respectively. a) false, 0, null b) true, 1, Null c) true, 1, null d) true, 0, null e) false, 1, null 53. Given the declaration Circle x = new Circle(), which of the following statement is most accurate? a) x contains a reference to a Circle object. b) You can assign an int value to x. c) x contains an int value. d) x contains an object of the Circle type. 54. is invoked to create an object. a) The main method b) A method with the void return type c) A method with a return type d) A constructor 55. Which of the following statements are correct? (Choose all that apply.) a) Number i = 4.5; b) Double i = 4.5; c) Integer i = 4.5; d) Object i = 4.5; 56. *Which of the following classes are immutable? a) Integer b) String c) Double d) BigInteger e) BigDecimal 57. *Suppose A is an interface, B is a concrete class with a default constructor that implements A. Which of the following is correct? a) B b = new B(); b) A a = new A(); c) A a = new B(); d) B b = new A(); 58. *Suppose A is an abstract class, B is a concrete subclass of A, and both A and B have a default constructor. Which of the following is correct? a) B b = new B(); b) A a = new A(); c) B b = new A(); d) A a = new B(); 59. Given the class definition : class A { class A1 { } },which of the following is the correct way to create an instance of class A1 a) new A.A1() b) (new A()). new A.A1() c) new A(new A.A1() ) d) new A.A1(new A() ) 5

6 60. Which of the following class definitions defines a legal abstract class? a) public class abstract A { abstract void unfinished(); } b) class A { abstract void unfinished(); } c) class A { abstract void unfinished() { } } d) abstract class A { abstract void unfinished(); } 61. Inheritance means. a) that data fields should be declared private b) that a variable of supertype can refer to a subtype object c) that a class can extend another class d) that a class can contain another class 62. Encapsulation means that. a) a class can extend another class b) a class can contain another class c) data fields should be declared private d) a variable of supertype can refer to a subtype object 63. Polymorphism means that. a)a class can contain another class b) a variable of supertype can refer to a subtype object c) data fields should be declared private d) a class can extend another class 64. Which of the following classes cannot be extended? a) class A { private A();} b) class A { } c) class A { protected A();} d) final class A { } 65. The visibility of Java modifiers increases in which of the following order: a) private, package, protected, and public. b) private, protected, package, and public. c) package, private, protected, and public. d) package, protected, private, and public. 66. What modifier should you use on a class so that a class in the same package can access it but a class in a different package cannot access it? a) protected b) private c) public d) package (default). 67. Object-oriented programming allows you to derive new classes from existing classes. This is called. a) inheritance b) abstraction c) encapsulation d) generalization 68. If the statement S2 cause an exception (and all other Sk( k = 1..7) do not) in the following statement: try { S1; S2; S3; } catch(exception1 e1) { S4; } catch(exception3 e3) { throw new Exception3(); } } catch(exception2 e2) { S5; } finally { S6; } S7; Then which of the following statement sequences is the correct sequence of statements executed after S2, if the exception is of the type Exception3? Suppose that Exception2 is a superclass of Exception3 while Exception1 is not. a) S6 b) S7 c) S6,S7 d) S4,S6,S7 e) S4,S5,S6,S7 69. Which of the following method would cause compile error if we put the code : "L.add(e) ;" into their bodies? a) public <E> void m0(list<e> L, E e) { } b) public <E> void m1(list<? extends E> L, E e) { } c) public <E> void m2(list<? super E> L, E e) { } d) public void m2(list L, Object e) { } 6

7 70. *Which of the following methods can be called by "m(new ArrayList<String>(), new Object() ) " without causing compile error? a) public <E> void m(list<e> L, E e) { } b) public <E> void m(list<? extends E> L, E e) { } c) public <E> void m(list<? super E> L, E e) { } d) public void m2(list L, Object e) { } II 程式設計 (30 pts) 1. Given the following class : public class Sum implements Runnable { public int rlt, from, to; Sum(int f, int t) { from = f; to = t} public void run() { for(int k = from; k<= to; k++) rlt += k; } Suppose we want to compute ( ) using multithreads. Therefore we partition this task into two subtasks: task1 perform ( ) and task2 performs ( ). Now, with the Sum class given, try to design a method which would create and start two threads to perform each subtask, and finally, after they complete, combine their results to get the final one. public static void man() { Sum task1 = _new Sum(1,1000), task2 = new Sum(1001,2000) ; Thread t1 = new Thread(task1), t2 = _new Thread(task2) ; // start both threads t1.start(); t2.start(); //wait them to complete t1.join(); t2.join() int rlt = _task1.rlt + task2.rlt ; out.println( The sum from 1 to 2000 is + rlt); } 2. Design a method duplicate(list L), which, when given a list of objects, can return the set of all objects which occur more than one time in L. import java.uitl.*; static <E> Set<E> duplicate(list<? extends E> L){ Set<E> s1 = new HashSet<E>() ; Set<E> rlt = new HashSet<E>(); for(e e : L) { if( s1.contains(e) ) } rlt.add(e) ; else s1.add(e) ; } return rlt; 7