A directory of Objective Type Questions covering all the Computer Science subjects. Here you can access and discuss Multiple choice questions and answers for various compitative exams and interviews.

1. Which of the following statements are correct about an ArrayList collection that implements the IEnumerable interface?

1. The ArrayList class contains an inner class that implements the IEnumerator interface.
2. An ArrayList Collection cannot be accessed simultaneously by different threads.
3. The inner class of ArrayList can access ArrayList class's members.
4. To access members of ArrayList from the inner class, it is necessary to pass ArrayList class's reference to it.
5. Enumerator's of ArrayList Collection can manipulate the array.
a. 1 and 2 only
b. 1 and 3 and 4 only
c. 2 and 5 only
d. All of the above
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Answer: (b).1 and 3 and 4 only

2. How many enumerators will exist if four threads are simultaneously working on an ArrayList object?
a. 1
b. 3
c. 2
d. 4
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Answer: (d).4

3. In which of the following collections is the Input/Output index-based?

1. Stack
2. Queue
3. BitArray
4. ArrayList
5. HashTable
a. 1 and 2 only
b. 3 and 4 only
c. 5 only
d. 1, 2 and 5 only
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Answer: (b).3 and 4 only

4. In which of the following collections is the Input/Output based on a key?

1. Map
2. Stack
3. BitArray
4. HashTable
5. SortedList
a. 1 and 2 only
b. 2 and 3 only
c. 1, 2 and 3 only
d. 4 and 5 only
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Answer: (d).4 and 5 only

5. In a HashTable Key cannot be null, but Value can be.
a. True
b. False
c. Maybe
d. Can't say
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Answer: (a).True

6. Which of the following statements are correct about the C#.NET code snippet given below?

Stack st = new Stack();
st.Push("hello");
st.Push(8.2);
st.Push(5);
st.Push('b');
st.Push(true);
a. Dissimilar elements like "hello", 8.2, 5 cannot be stored in the same Stack collection.
b. Boolean values can never be stored in Stack collection.
c. In the fourth call to Push(), we should write "b" in place of 'b'.
d. This is a perfectly workable code.
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Answer: (d).This is a perfectly workable code.

7. Which of the following statements are correct about the Stack collection?

1. It can be used for evaluation of expressions.
2. All elements in the Stack collection can be accessed using an enumerator.
3. It is used to maintain a FIFO list.
4. All elements stored in a Stack collection must be of similar type.
5. Top-most element of the Stack collection can be accessed using the Peek() method.
a. 1 and 2 only
b. 3 and 4 only
c. 1, 2 and 5 only
d. All of the above
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Answer: (c).1, 2 and 5 only

8. A HashTable t maintains a collection of names of states and capital city of each state. Which of the following is the correct way to find out whether "Kerala" state is present in this collection or not?
a. t.ContainsKey("Kerala");
b. t.HasValue("Kerala");
c. t.HasKey("Kerala");
d. t.ContainsState("Kerala");
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Answer: (a).t.ContainsKey("Kerala");

9. Which of the following is the correct way to access all elements of the Queue collection created using the C#.NET code snippet given below?

Queue q = new Queue(); 
q.Enqueue("Sachin"); 
q.Enqueue('A'); 
q.Enqueue(false); 
q.Enqueue(38); 
q.Enqueue(5.4);
a. IEnumerator e;
e = q.GetEnumerator();
while (e.MoveNext())
Console.WriteLine(e.Current);
b. IEnumerable e;
e = q.GetEnumerator();
while (e.MoveNext())
Console.WriteLine(e.Current);
c. IEnumerator e;
e = q.GetEnumerable();
while (e.MoveNext())
Console.WriteLine(e.Current);
d. IEnumerator e;
e = Queue.GetEnumerator();
while (e.MoveNext())
Console.WriteLine(e.Current);
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Answer: (a).IEnumerator e;
e = q.GetEnumerator();
while (e.MoveNext())
Console.WriteLine(e.Current);

10. Which of the following is NOT an interface declared in System.Collections namespace?
a. IComparer
b. IEnumerable
c. IEnumerator
d. IDictionaryComparer
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Answer: (d).IDictionaryComparer

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