複選題
211 

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 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 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 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  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 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] (AB) [606, 608, 610, 612, 629] [608, 610, 629]

215 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 (AB) An exception is thrown at runtime.

複選題219 Which two can be results? (Choose two.) (A) java.lang.RuntimeException: Problem (B)  (C) (D) (E) 

220 Which factor or factors  1. It is possible for more than two threads to deadlock at once.  2. The JVM implementation guarantees that multiple threads cannot enter into a deadlocked state.  3. Deadlocked threads release once their sleep() method's sleep duration has expired.  4. Deadlocking can occur only when the wait(), notify() and notifyAll() methods are used incorrectly.  5. It is possible for a single-threaded application to deadlock if synchronized blocks are used incorrectly.  6. If a piece of code is capable of deadlocking, you cannot eliminate the possibility of deadlocking by inserting invocations of Thread.yield(). (A) 16 (B) 25 (C) 34 (D) 12