Java MCQ – Collections – Part 3

This collection of Java Multiple Choice Questions and Answers (MCQs): Quizzes & Practice Tests with Answer focuses on “Java Collections”.
 

1. Which class stores items as a key-value pair?

A Arraylist

B LinkedHashSet

C TreeMap

D TreeSet

2. Which is faster and uses less memory?

A ListEnumeration

B Iterator

C ListIterator

D Enumeration

3. What is the output of the following code?

import java.util.*;

public class Main 
{
	public static void main(String args[]) 
	{
		int tab[] = new int [6];
		
		for (int i = 6; i > 0; i--)
			tab[6-i] = i;
		
		Arrays.fill(tab, 1, 5, 0);
		
		for (int i = 0; i < 6 ; i++)
			System.out.print(tab[i]);
	}
}

A 611110

B 543210

C 654321

D 600001

4. Which of these is an incorrect form of using the max() method to get the maximum element?

A max(Collection c, Comparator comp)

B max(Collection c)

C max(Comparator comp)

D max(List c)

5. Which of these methods can mix all the elements of a list?

A rand()

B srand()

C randomize()

D shuffle()

import java.util.*; 
  
public class Main { 
    public static void main(String[] args) 
    { 
        ArrayList<String> list = new ArrayList<String>(); 
		
        list.add("A"); 
        list.add("B"); 
        list.add("C"); 
 
        System.out.println("Before mixing the elements: "+list);
		
        Collections.shuffle(list); 
		
        System.out.println("After mixing the elements: "+list);
    } 
}

Before mixing the elements: [A, B, C]
After mixing the elements: [C, A, B]

6. Which of the following methods can convert an object to a list?

A SetList()

B ConvertList()

C singletonList()

D CopyList()

7. Default capacity of a vector is ___

A 10

B 12

C 8

D 16

8. Which one is best suited for a multi-threaded environment?

A WeakHashMap

B Hashtable

C HashMap

D ConcurrentHashMap

9. Which of the following interface does NOT implement the Collection interface?

A List

B Map

C Set

D None of the above

10. Default capacity of an ArrayList is ___

A 12

B 10

C 8

D 16

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