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)

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)

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()；

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]

215. Given: 1. import java.util.*； 2. 3. public class LetterASort{ 4. public static void main(String[] args){ 5. ArrayList＜String＞ strings = new ArrayList＜String＞()； 6. strings.add("aAaA")； 7. strings.add("AaA")； 8. strings.add("aAa")； 9. strings.add("AAaa")； 10. Collections.sort(strings)； 11. for(String s : strings){System.out.print(s + " ")；} 12. } 13. }What is the result?(A)Compilation fails.(B) aAaA aAa AAaa AaA (C)AAaa AaA aAa aAaA (D) AaA AAaa aAaA aAa(E) aAa AaA aAaA AAaa

複選題219. Given: 1. public class Threads2 implements Runnable{ 2. 3. public void run(){ 4. System.out.println("run.")； 5. throw new RuntimeException("Problem")； 6. } 7. public static void main(String[] args){ 8. Thread t = new Thread(new Threads2())； 9. t.start()； 10. System.out.println("End of method.")； 11. } 12. } Which two can be results? (Choose two.) (A) java.lang.RuntimeException: Problem (B) run. java.lang.RuntimeException: Problem (C) End of method. java.lang.RuntimeException: Problem (D) End of method. run. java.lang.RuntimeException: Problem (E) run. java.lang.RuntimeException: Problem End of method.

221. Given: 7. void waitForSignal(){ 8. Object obj = new Object()； 9. synchronized(Thread.currentThread()){ 10. obj.wait()； 11. obj.notify()； 12. } 13. } Which statement is true? (A) This code can throw an InterruptedException. (B) This code can throw an IllegalMonitorStateException. (C) This code can throw a TimeoutException after ten minutes. (D) Reversing the order of obj.wait() and obj.notify() might cause this method to complete normally. (E) A call to notify() or notifyAll() from another thread might cause this method to complete normally.