193. Given that the elements of a PriorityQueue are ordered according to natural ordering, and: 

2. import java.util.*； 

3. public class GetInLine{ 

4. public static void main(String[] args){

 5. PriorityQueue＜String＞ pq = new PriorityQueue＜String＞()； 

6. pq.add("banana")； 

7. pq.add("pear")； 

8. pq.add("apple")； 

9. System.out.println(pq.poll() + " " + pq.peek())； 

10. } 

11. } 

What is the result?
(A) apple pear
(B) banana pear
(C) apple apple
(D) apple banana
(E) banana banana

187. Given: 1. public class Score implements Comparable＜Score＞{ 2. private int wins, losses； 3. public Score(int w, int l){wins = w； losses = l；} 4. public int getWins(){return wins；} 5. public int getLosses(){return losses；} 6. public String toString(){ 7. return "＜" + wins + "," + losses + "＞"； 8. } 9. //insert code here 10. } Which method will complete this class? (A) public int compareTo(Object o){/* more code here */} (B) public int compareTo(Score other){/* more code here */} (C) public int compare(Score s1, Score s2){/* more code here */} (D) public int compare(Object o1, Object o2){/* more code here */}

189. Given: 23. Object[] myObjects = { 24. new Integer(12), 25. new String("foo"), 26. new Integer(5), 27. new Boolean(true) 28. }； 29. Arrays.sort(myObjects)； 30. for(int i=0； i＜myObjects.length； i++){ 31. System.out.print(myObjects[i].toString())； 32. System.out.print(" ")； 33. } What is the result? (A) Compilation fails due to an error in line 23. (B) Compilation fails due to an error in line 29. (C) A ClassCastException occurs in line 29. (D) A ClassCastException occurs in line 31. (E) The value of all four objects prints in natural order.

190. Given: 1. import java.util.*； 2. public class WrappedString{ 3. private String s； 4. public WrappedString(String s){this.s = s；} 5. public static void main(String[] args){ 6. HashSet＜Object＞ hs = new HashSet＜Object＞()； 7. WrappedString ws1 = new WrappedString("aardvark")； 8. WrappedString ws2 = new WrappedString("aardvark")； 9. String s1 = new String("aardvark")； 10. String s2 = new String("aardvark")；11. hs.add(ws1)； hs.add(ws2)； hs.add(s1)； hs.add(s2)； 12. System.out.println(hs.size())； }} What is the result? (A) 0 (B) 1 (C) 2 (D) 3 (E) 4

複選題192. Given: 3. import java.util.*； 4. public class G1{ 5. public void takeList(List＜? extends String＞ list){ 6. //insert code here 7. } 8. } Which three code fragments, inserted independently at line 6, will compile? (Choose three.) (A) list.add("foo")； (B) Object o = list； (C) String s = list.get(0)； (D) list = new ArrayList＜String＞()； (E) list = new ArrayList＜Object＞()；

194. Given:        enum Example{ONE, TWO, THREE} Which statement is true? (A) The expressions (ONE == ONE) and ONE .equals(ONE) are both guaranteed to be true. (B) The expression (ONE ＜ TWO) is guaranteed to be true and ONE.compareTo(TWO) is guaranteed to be less than one. (C) The Example values cannot be used in a raw javautil.HashMap； instead, the programmer must use a java.util.EnumMap. (D) The Example values can be used in a java.util.SortedSet, but the set will NOT be sorted because enumerated types do NOT implement java.lang.Comparable.

195. Given: 3. import java.util.*； 4. public class Mapit{ 5. public static void main(String[] args){ 6. Set＜Integer＞ set = new HashSet＜Integer＞()； 7. Integer i1 = 45； 8. Integer i2 = 46； 9. set.add(i1)； 10. set.add(i1)； 11. set.add(i2)； System.out.print(set.size() + " ")； 12. set.remove(i1)； System.out.print(set.size() + " ")； 13. i2 = 47； 14. set.remove(i2)； System.out.print(set.size() + " ")； 15. } 16. } What is the result? (A) 2 1 0 (B) 2 1 1 (C) 3 2 1 (D) 3 2 2 (E) Compilation fails.

196. Given: 34. HashMap props = new HashMap()； 35. props.put("key45", "some value")； 36. props.put("keyl2", "some other value")； 37. props.put("key39", "yet another value")； 38. Set s = props.keySet()； 39. //insert code here What inserted at line 39, will sort the keys in the props HashMap? (A) Arrays.sort(s)； (B) s = new TreeSet(s)； (C) Collections.sort(s)； (D) s = new SortedSet(s)；

197. Given: 11. public static Collection get(){ 12. Collection sorted = new LinkedList()； 13. sorted.add("B")； sorted.add("C")； sorted.add("A")； 14. return sorted； 15. } 16. public static void main(String[] args){ 17. for(Object obj : get()){ 18. System.out.print(obj + ", ")； 19. } 20. } What is the result? (A) A, B, C, (B) B, C, A, (C) Compilation fails. (D) The code runs with no output (E) An exception is thrown at runtime.

198. Given: 11. public static Iterator reverse(List list){ 12. Collections.reverse(list)； 13. return list.iterator()； 14. }  15. public static void main(String[] args){ 16. List list= new ArrayList()； 17. list.add("1")； list.add("2")； list.add("3")； 18. for(Object obj : reverse(list)) 19. System.out.print(obj + ", ")； 20. } What is the result? (A) 3, 2, 1, (B) 1, 2, 3, (C) Compilation fails. (D) The code runs with no output. (E) An exception is thrown at runtime.

200. Given: 11. public class Person{ 12. private String name； 13. public Person(String name){ 14. this.name = name；  15. } 16. public boolean equals(Object o){ 17. if(!(o instanceof Person)) return false； 18. Person p = (Person)o； 19. return p.name.equals(this.name)； 20. } 21. } Which statement is true? (A) Compilation fails because the hashCode method is not overridden. (B) A HashSet could contain multiple Person objects with the same name. (C) All Person objects will have the same hash code because the hashCode method is not overridden. (D) If a HashSet contains more than one Person object with name="Fred", then removing another Person, also with name="Fred", will remove them all.