189 

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.

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

190 What is the result? (A) 0 (B) 1 (C) 2 (D) 3 (E) 4 (AB) Compilation fails. (AC) An exception is thrown at runtime.

191 Which two, inserted at line 11, will allow the code to compile? (Choose two.)   1. public class MinMax＜?＞{  2. public class MinMax＜? extends Number＞{  3. public class MinMax＜N extends Object＞{  4. public class MinMax＜N extends Number＞{  5. public class MinMax＜? extends Object＞{  6. public class MinMax＜N extends Integer＞{ (A) 15 (B) 23 (C) 46 (D) 56

複選題192 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＞();

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

194 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 java.util.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 What is the result? (A) 2 1 0 (B) 2 1 1 (C) 3 2 1 (D) 3 2 2 (E) Compilation fails. (AB) An exception is thrown at runtime.