Java Multiple Choice Questions & Answers on Collection Framework Overview for Freshers

1. Which of these packages contain all the collection classes?

a) java.lang
b) java.util
c) java.net
d) java.awt

Answer: b

2. Which of these classes is not part of Java’s collection framework?

a) Maps
b) Array
c) Stack
d) Queue

Answer: a

Explanation: Maps is not a part of collection framework.

3. Which of these interface is not a part of Java’s collection framework?

a) List
b) Set
c) SortedMap
d) SortedList

Answer: d

Explanation: SortedList is not a part of collection framework.

4. Which of these methods deletes all the elements from invoking collection?

a) clear()
b) reset()
c) delete()
d) refresh()

Answer: a

Explanation: clear() method removes all the elements from invoking collection.

5. What is Collection in Java?

a) A group of objects
b) A group of classes
c) A group of interfaces
d) None of the mentioned

Answer: a

Explanation: A collection is a group of objects, it is similar to String Template Library (STL) of C++ programming language.

6. What is the output of this program?

1.     import java.util.*;

2.     class Array {

3.         public static void main(String args[]) {

4.             int array[] = new int [5];

5.             for (int i = 5; i > 0; i--)

6.                 array[5-i] = i;

7.             Arrays.fill(array, 1, 4, 8);

8.             for (int i = 0; i < 5 ; i++)

9.                 System.out.print(array[i]);

10.         }

11.     }

a) 12885
b) 12845
c) 58881
d) 54881

Answer: c

Explanation: array was containing 5,4,3,2,1 but when method Arrays.fill(array, 1, 4, 8) is called it fills the index location starting with 1 to 4 by value 8 hence array becomes 5,8,8,8,1.

7. What is the output of this program?

1.     import java.util.*;

2.     class vector {

3.         public static void main(String args[]) {

4.             Vector obj = new Vector(4,2);

5.             obj.addElement(new Integer(3));

6.             obj.addElement(new Integer(2));

7.             obj.addElement(new Integer(5));

8.             obj.removeAll(obj);

9.             System.out.println(obj.isEmpty());

10.         }

11.     }

a) 0
b) 1
c) true
d) false

Answer: c

Explanation: firstly elements 3, 2, 5 are entered in the vector obj, but when obj.removeAll(obj); is executed all the elements are deleted and vector is empty, hence obj.isEmpty() returns true.

8. What is the output of this program?

1.     import java.util.*;

2.     class stack {

3.         public static void main(String args[]) {

4.             Stack obj = new Stack();

5.             obj.push(new Integer(3));

6.             obj.push(new Integer(2));

7.             obj.pop();

8.             obj.push(new Integer(5));

9.           System.out.println(obj);

10.         }

11.     }

a) [3, 5]

b) [3, 2] 

c) [3, 2, 5] 

d) [3, 5, 2] 

Answer: a

Explanation: push() and pop() are standard functions of the class stack, push() inserts in the stack and pop removes from the stack. 3 & 2 are inserted using push() the pop() is used which removes 2 from the stack then again push is used to insert 5 hence stack contains elements 3 & 5.

9. What is the output of this program?

1.     import java.util.*;

2.     class hashtable {

3.         public static void main(String args[]) {

4.             Hashtable obj = new Hashtable();

5.             obj.put("A", new Integer(3));

6.             obj.put("B", new Integer(2));

7.             obj.put("C", new Integer(8));

8.             obj.remove(new String("A"));

9.             System.out.print(obj);

10.         }

11.     }

a) {C=8, B=2}
b) [C=8, B=2] 

c) {A=3, C=8, B=2}
d) [A=3, C=8, B=2] 

Answer: b

10. What is the output of this program?

1.     import java.util.*;

2.     class Bitset {

3.         public static void main(String args[]) {

4.             BitSet obj = new BitSet(5);

5.             for (int i = 0; i < 5; ++i)

6.                 obj.set(i);

7.             obj.clear(2);

8.             System.out.print(obj);

9.         }

10.     }

a) {0, 1, 3, 4}
b) {0, 1, 2, 4}
c) {0, 1, 2, 3, 4}
d) {0, 0, 0, 3, 4}

Answer: a