複選題
175 Which two scenarios are NOT safe to replace a StringBuffer object with a StringBuilder object? (Choose two.)
(A) When using versions of Java technology earlier than 5.0.
(B) When sharing a StringBuffer among multiple threads.
(C) When using the java.io class StringBufferInputStream.
(D) When you plan to reuse the StringBuffer to build more than one string.
(E) Enitiation of separate design processes to the separation of users

171 What is the result? (A) a b c (B) 1 2 3 (C) a1b2c3 (D) a1 b2 c3 (E) Compilation fails. (AB) The code runs with no output. (AC) An exception is thrown at runtime.

172 What creates the appropriate DateFormat object and adds a day to the Date object? (A) (B)  (C) (D) 

173 What is the result? (A) int Long (B) Short Long (C) Compilation fails. (D) An exception is thrown at runtime.

174 What is the result if this code is run on December 14, 2000? (A) The value of s is 14-dic-2000. (B) The value of s is Dec 14, 2000. (C) An exception is thrown at runtime. (D) Compilation fails because of an error in line 13.

177 What is the result? (A) 0 (B) 1 (C) 4 (D) Compilation fails. (E) An exception is thrown at runtime.

178 Which change can you make to Target without affecting Client? (A) Line 4 of class Target can be changed to return i++; (B) Line 2 of class Target can be changed to private int i = 1; (C) Line 3 of class Target can be changed to private int addOne(){ (D) Line 2 of class Target can be changed to private Integer i = 0;

185 Which statement is true? (A) The equals method does NOT properly override the Object.equals method. (B) Compilation fails because the private attribute p.name cannot be accessed in line 5. (C) To work correctly with hash-based data structures, this class must also implement the hashCode method. (D) When adding Person objects to a java.util.Set collection, the equals method in line 4 will prevent duplicates.

複選題186 Which two statements are true about the hashCode method? (Choose two.) (A) The hashCode method for a given class can be used to test for object equality and object inequality for that class. (B) The hashCode method is used by the java.util.SortedSet collection class to order the elements within that set. (C) The hashCode method for a given class can be used to test for object inequality, but NOT object equality, for that class. (D) The only important characteristic of the values returned by a hashCode method is that the distribution of values must follow a Gaussian distribution. (E) The hashCode method is used by the java.util.HashSet collection class to group the elements within that set into hash buckets for swift retrieval.

187  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 */}

188 What three changes allow the class to be used with generics and avoid an unchecked warning? (Choose three.)   1. Remove line 14.  2. Replace line 14 with "int i = iter.next();".  3. Replace line 13 with "for(int i : intList){".  4. Replace line 13 with "for(Iterator iter : intList){".   5. Replace the method declaration with "sum(List＜int＞ intList)".  6. Replace the method declaration with "sum(List＜Integer＞ intList)". (A) 123 (B) 246 (C) 136 (D) 456