9:27 AM
Anonymous
Q1. Given:
34. HashMap
props = new HashMap();
35. props.put("key45",
"some value");
36. props.put("key12",
"some other value");
37. props.put("key39",
"yet another value");
38. Set
s = props.keySet();
39. //
insert code here
What, inserted at line 39, will sort the
keys in the props HashMap?
A. Arrays.sort(s); B. s
= new TreeSet(s);
C. Collections.sort(s); D. s = new SortedSet(s);
Q2. Click the Exhibit button.
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.
Q3. Given:
23. Object [] myObjects = {
24. new
Integer(12),
25. new
String("foo"),
26. new
Integer(5),
27. new
Boolean(true)
28. };
29. Arrays.sort(myObjects);
30. for(int i=0; i<myObjects.length; i++)
{
31. System.out.print(myObjects[i].toString());
32. System.out.print("
");
33. }
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.
Q4. Given:
1. public
class Person {
2. private String name;
3. public Person(String name) { this.name =
name; }
4. public boolean equals(Person p) {
5. return
p.name.equals(this.name);
6. }
7. }
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.
Q5. Given:
import java.util.*;
public class Old {
public static Object
get0(List list) {
return list.get(0);
}
}
Which three will compile successfully?
(Choose three.)
A. Object o = Old.get0(new LinkedList());
B. Object
o = Old.get0(new LinkedList<?>());
C. String
s = Old.get0(new LinkedList<String>());
D. Object o = Old.get0(new
LinkedList<Object>());
E. String s = (String)Old.get0(new
LinkedList<String>());
Q6. 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();
Q7. Given:
public static Collection get() {
Collection
sorted = new LinkedList();
sorted.add("B");
sorted.add("C");
sorted.add("A");
return
sorted;
}
public static void main(String[] args) {
for
(Object obj: get())
System.out.print(obj
+ ", ");
}
What is the result?
A. A,
B, C, B. B,
C, A, C. Compilation
fails.
D. The
code runs with no output. E. An exception is thrown at runtime.
Q8. Given:
public static Iterator reverse(List list) {
Collections.reverse(list);
return
list.iterator();
}
public static void main(String[] args) {
List
list = new ArrayList();
list.add("1");
list.add("2");
list.add("3");
for
(Object obj: reverse(list))
System.out.print(obj
+ ", ");
}
What is the result?
A. 3,
2, 1, B. 1, 2, 3, C. Compilation fails.
D. The code runs with no output.
E. An
exception is thrown at runtime.
Q9. Given:
import java.util.*;
public class PQ {
public static void
main(String[] args) {
PriorityQueue<String>
pq = new PriorityQueue<String>();
pq.add("carrot");
pq.add("apple");
pq.add("banana");
System.out.println(pq.poll()
+ ":" + pq.peek());
}
}
What is the result?
A. apple:apple B. carrot:apple C. apple:banana
D. banana:apple E. carrot:carrot F.
carrot:banana
Q10. Given:
import java.util.*;
public class WrappedString {
private
String s;
public
WrappedString(String s) { this.s = s; }
public
static void main(String[] args) {
HashSet<Object>
hs = new HashSet<Object>();
WrappedString
ws1 = new WrappedString("aardvark");
WrappedString
ws2 = new WrappedString("aardvark");
String
s1 = new String("aardvark");
String
s2 = new String("aardvark");
hs.add(ws1);
hs.add(ws2);
hs.add(s1);
hs.add(s2);
System.out.println(hs.size());
}
}
What is the result?
A. 0 B. 1 C.
2 D. 3 E.
4 F.
Compilation fails.
G. An
exception is thrown at runtime.
Q11. Given:
public class Key {
private long id1;
private long id2;
// class Key methods
}
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
boolean equals(Key k)
C. public
int compareTo(Object o)
D. public
boolean equals(Object o)
E. public
boolean compareTo(Key k)
Q12 Given a pre-generics implementation of a
method:
11. public
static int sum(List list) {
12. int sum = 0;
13. for
( Iterator iter = list.iterator(); iter.hasNext(); ) {
14. int
i = ((Integer)iter.next()).intValue();
15. sum
+= i;
16. }
17. return
sum;
18. }
Which three changes must be made to the
method sum to use generics? (Choose three.)
A. remove line 14
B. replace
line 14 with "int i = iter.next();"
C. replace line 13 with "for (int i :
intList) {"
D. replace
line 13 with "for (Iterator iter : intList) {"
E. replace
the method declaration with "sum(List<int> intList)"
F. replace the method declaration with
"sum(List<Integer> intList)"
Q13. What are major enhancements in 1.4 version
of collection frame work?
A. LinkedHashSet B. LinkedHashMap C. IdentityHashMap D.
WeakHashSet
Q14. We are planning to do an indexed search in
a list of objects. Which of the 2 Java collections should you use
A. ArrayList B. LinkedList
Q15. Which of the following are true about List
interface?
A. List interface is a
child interface of Collections interface
B.
Duplicates are
allowed
C.
Insertion order is
preserved
D. List is a sub
interface of Collection class
Q16. Which of the following are true about Set
interface?
A. Set is a child
interface of Collection class.
B.
It can be used to
represent a group of individual objects as a single entity
C.
Duplicate objects
are not allowed.
D.
Insertion order is
not preserved
Q17. Which of the following are true about NavigableSet?
A.
It is child
interface of SortedSet and provides several utility methods for navigation
purposes
B. It allows duplicates
C. Insertion order is not
preserved
D.
It is introduced in
1.6 version
Q18. Which of the following are true about Map
interface?
A.
Remember it is not a
child Interface of Collection Interface and hence Map and Collection Interfaces
doesn’t have any relationship.
B. It cannot be used
for representing a group of Objects as key, value pairs.
C. Both keys and values
need not be objects
D.
Keys can’t be
duplicated but values can be duplicated.
E.
It has introduced in 1.2 version
Q19. Which
of the following are true about ArrayList class?
A.
The underlying data
structure is resizable or growable array.
B. Duplicates are not
allowed
C. Heterogeneous
objects are not allowed
D. null insertion is
not possible
E.
This class
implements RandomAccess, Serializable, Cloneable interfaces
Q20. Which of the following are true about
LinkedList class?
A.
Underlying data Structure
is DoubleLinkedList
B.
Allows duplicates
objects
C. Insertion order is not
preserved
D. Does not allow
heterogeneous objects
E.
null insertion is
possible
F. This class
implements RandomAccess, Serializable, Cloneable interfaces
Q21. Which of the following are true about
Vector class?
A.
The underlying data
structure is resizable or growable array.
B. Duplicates are not allowed
C. Heterogeneous
objects are not allowed
D.
It is a implemented
class for List interface
E. null insertion is
possible
F. Vector class object
is not thread safe.
Q22. Which of the following are true Iterator
and ListIterator?
A.
ListIterator
is not the child interface of the Iterator
B.
Iterator is the
single direction cursor where as ListIterator is bidirectional cursor.
C.
While iterating the
elements by Iterator we can perform only read and remove operations. But by
using ListIterator we can perform read, removal, replace and addition of new
objects also.
D.
Iterator is
applicable for every Collecton implemented class object but ListIterator is
applicable only for List implemented class objects.
E.
ListIterator
cannot be get by using listIterator() method of List interface
Q23. Which of the following are true about
HashSet class?
A.
Insertion order is
based on hashcode of the object hence insertion order is not preserved
B.
Best suitable if frequent operation is search operations
C.
HashSet class
implements Serializable and Cloneable
D. It is implementation
class for List interface
E. Heterogeneous
objects are not allowed
Q24. Which of the following are true about TreeMap?
A.
The underlying data
structure is RED-BLACK Tree
B. Duplicates keys are
allowed but values can be duplicated.
C.
Insertion order is
preserved because insertion is based on some sorting order
D.
For non empty
TreeMap if we are trying to insert null keys we will get NullPointerException
E. There are no
restrictions for null values.
Q25. Which
of the following are true about Hashtable
A. Duplicates keys are
allowed but duplicate values are allowed
B. null insertion is
possible for both keys and values
C.
all methods are
synchronized
D. insertion order is
preserved because it is based on
hashcode of keys
E.
heterogeneous
Objects are allowed for both keys and values
Q26. A programmer has an algorithm that requires
a java.util.List that provides an efficient implementation of add(0, object), but does NOT need to
support quick random access. What supports these requirements?
A.
java.util.Queue
B.
java.util.ArrayList
C.
java.util.LinearList
D. java.util.LinkedList
Q27. 5. import
java.util.Date;
6. import
java.text.DateFormat;
21. DateFormat
df;
22. Date
date = new Date();
23. //
insert code here
24. String
s = df.format(date);
Which code fragment, inserted at
line 23, allows the code to compile?
A.
df = new DateFormat();
B.
df = Date.getFormat();
C.
df = date.getFormat();
D.
df = DateFormat.getFormat();
E. df =
DateFormat.getInstance();
Q28. Given:
10.
interface A { void x(); }
11.
class B implements A { public void x() {} public void y() {} }
12.
class C extends B { public void x() {} }
And:
20.
java.util.List<A> list = new java.util.ArrayList<A>();
21.
list.add(new B());
22.
list.add(new C());
23.
for (A a : list) {
24.
a.x();
25.
a.y();
26.
}
What is the result?
A. The code runs with no output.
B. An exception is thrown at runtime.
C. Compilation fails because of an error in line
20.
D. Compilation fails because of an error in line
21.
E. Compilation fails because of an error in line
23.
F. Compilation fails because of
an error in line 25.
Q29. import java.util.*;
public class Mapit {
public static void
main(String[] args) {
Set<Integer>
set = new HashSet<Integer>();
Integer i1 =
45;
Integer i2 =
46;
set.add(i1);
set.add(i1);
set.add(i2);
System.out.print(set.size()
+ " ");
set.remove(i1);
System.out.print(set.size()
+ " ");
i2 = 47;
set.remove(i2);
System.out.print(set.size()
+ " ");
}
}
What is the result?
A. 2 1 0 B. 2 1 1 C.
3 2 1 D. 3 2 2 E. Compilation fails.
F. An exception is thrown at
runtime.
Q30. 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.
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