208. Given: 

1. import java.util.*； 

2. public class Example{ 

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

4. //insert code here 

5. set.add(new Integer(2))； 

6. set.add(new Integer(1)), 

7. System.out.println(set)； 

8. } 

9. } 

Which code, inserted at line 4, guarantees that this program will output [1, 2]?
(A) Set set = new TreeSet()；
(B) Set set = new HashSet()；
(C) Set set = new SortedSet()；
(D) List set = new SortedList()；
(E) Set set = new LinkedHashSet()；

204. Given: 11. public class Person{ 12. private name； 13. public Person(String name){ 14. this.name = name； 15. } 16. public int hashCode(){ 17. return 420； 18. } 19. } Which statement is true? (A) The time to find the value from HashMap with a Person key depends on the size of the map. (B) Deleting a Person key from a HashMap will delete all map entries for all keys of type Person. (C) Inserting a second Person object into a HashSet will cause the first Person object to be removed as a duplicate. (D) The time to determine whether a Person object is contained in a HashSet is constant and does NOT depend on the size of the map.

205. Given: 12. import java.util.*； 13. public class Explorer2{ 14. public static void main(String[] args){ 15. TreeSet＜Integer＞ s = new TreeSet＜Integer＞()； 16. TreeSet＜Integer＞ subs = new TreeSet＜Integer＞()； 17. for(int i=606； i＜613； i++) 18. if(i%2 == 0) s.add(i)； 19. subs = (TreeSet)s.subSet(608, true, 611, true)； 20. s.add(629)； 21. System.out.println(s + " " + subs)； 22. } 23. } What is the result? (A) Compilation fails. (B) An exception is thrown at runtime. (C) [608, 610, 612, 629] [608, 610] (D) [608, 610, 612, 629] [608, 610, 629] (E) [606, 608, 610, 612, 629] [608, 610]

206. Given: 1. public class Drink implements Comparable{2. public String name； 3. public int compareTo(Object o){ 4. return 0； 5. } 6. } and: 20. Drink one = new Drink()； 21. Drink two = new Drink()； 22. one.name = "Coffee"； 23. two.name = "Tea"； 24. TreeSet set = new TreeSet()； 25. set.add(one)； 26. set.add(two)； A programmer iterates over the TreeSet and prints the name of each Drink object. What is the result? (A) Tea (B) Coffee (C) Coffee Tea (D) Compilation fails. (E) The code runs with no output.

207. A programmer must create a generic class MinMax and the type parameter of MinMax must implement Comparable. Which implementation of MinMax will compile? (A) (B) (C) (D)

209. Given:  1. import java.util.*； 2. public class TestSet{ 3. enum Example{ONE, TWO, THREE} 4. public static void main(String[] args){ 5. Collection coll = new ArrayList()； 6. coll.add(Example.THREE)； 7. coll.add(Example.THREE)； 8. coll.add(Example.THREE)； 9. coll.add(Example.TWO)； 10. coll.add(Example.TWO)； 11. coll.add(Example.ONE) 12. Set set = new HashSet(coll)； 13. } 14. } Which statement is true about the set variable on line 12? (A) The set variable contains all six elements from the coll collection, and the order is guaranteed to be preserved. (B) The set variable contains only three elements from the coll collection, and the order is guaranteed to be preserved. (C) The set variable contains all six elements from the coll collection, but the order is NOT guaranteed to be preserved. (D) The set variable contains only three elements from the coll collection, but the order is NOT guaranteed to be preserved.

210. Given: 11. public class Person{ 12. private String name, comment； 13. private int age； 14. public Person(String n, int a, String c){ 15. name = n； age = a； comment = c； 16. } 17. public boolean equals(Object o){ 18. if (!(0 instanceof Person)) return false； 19. Person p = (Person)o； 20. return age == p.age && name.equals(p.name)； 21. } 22. } What is the appropriate definition of the hashCode method in class Person? (A) return super.hashCode()； (B) return name.hashcode() + age * 7； (C) return name.hashCode() + comment.hashCode() / 2； (D) return name.hashCode() + comment.hashCode() / 2- age * 3；

複選題211. Given: 11. public class Key{ 12. private long id1, 13. private long id2； 14. 15. //class Key methods 16. } A programmer is developing a class Key, that will be used as a key in a standard java.util.HashMap. Which two methods should be overridden to assure that Key works correctly as a key? (Choose two.) (A) public int hashCode() (B) public void hashCode() (C) public int compareTo(Object o) (D) public boolean equals(Object o) (E)public boolean compareTo(Key k)

複選題212. Given: 3. import java.util.*； 4. public class Hancock{ 5. //insert code here 6. list.add("foo")； 7. } 8. } Which two code fragments, inserted independently at line 5, will compile without warnings? (Choose two.) (A) public void addStrings(List list){ (B) public void addStrings(List＜String＞ list){ (C) public void addStrings(List＜? super String＞ list){ (D) public void addStrings(List＜? extends String＞ list){

複選題213. Given a class whose instances, when found in a collection of objects, are sorted by using the compareTo() method, which two statements are true? (choose two.) (A) The class implements java.lang.Comparable. (B) The class implements java.util.Comparator. (C) The interface used to implement sorting allows this class to define only one sort sequence. (D) The interface used to implement sorting allows this class to define many different sort sequences.

214. Given: 12. import java.util.*；13. public class Explorer3{ 14. public static void main(String[] args){ 15. TreeSet＜Integer＞ s = new TreeSet＜Integer＞()； 16. TreeSet＜Integer＞ subs = new TreeSet＜Integer＞()； 17. for(int i=606； i＜613； i++) 18. if(i%2 == 0) s.add(i)； 19. subs = (TreeSet)s.subSet(608, true, 611, true)； 20. subs.add(629)； 21. System.out.println(s + " " + subs)； 22. } 23. } What is the result? (A) Compilation fails. (B) An exception is thrown at runtime. (C) [608, 610, 612, 629] [608, 610] (D) [608, 610, 612, 629] [608, 610, 629] (E) [606, 608, 610, 612, 629] [608, 610]