Java Set and HashSet Quiz

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Question 1

Which of the following statements about Set in Java is correct?

A
Set allows duplicate elements
B
Set maintains insertion order
C
Set does not allow duplicate elements
D
Set allows duplicate elements but ignores null values

Question 2

Which of the following describes how HashSet stores elements in Java?

A
It uses a balanced binary tree to store elements.
B
It stores elements in a hash table using their hash codes.
C
It stores elements in a linked list for fast insertion.
D
It uses a stack-based structure for element management.

Question 3

What will be the output of the following code?

Java

import java.util.*;
public class Test {
    public static void main(String[] args) {
        Set<String> set = new HashSet<>();
        set.add("Java");
        set.add("Python");
        set.add("Java");
        System.out.println(set);
    }
}

A
[Java, Python, Java]
B
[Java, Python]
C
[Python, Java, Java]
D
Compilation Error

Question 4

What is the time complexity of contains() operation in HashSet?

A
O(1)
B
O(n)
C
O(log n)
D
O(n log n)

Question 5

What will be the output of the following code?

Java

import java.util.*;
public class Test {
    public static void main(String[] args) {
        Set<Integer> set = new TreeSet<>();
        set.add(5);
        set.add(3);
        set.add(8);
        set.add(1);
        System.out.println(set);
    }
}

A
[5, 3, 8, 1]
B
[1, 3, 5, 8]
C
[8, 5, 3, 1]
D
Compilation Error

Question 6

What is the key difference between LinkedHashSet and HashSet?

A
LinkedHashSet maintains insertion order, while HashSet does not
B
HashSet is synchronized, while LinkedHashSet is not
C
LinkedHashSet allows duplicate elements, while HashSet does not
D
LinkedHashSet is slower than HashSet for all operations

Question 7

What happens when you insert null in a TreeSet?

A
null is allowed and stored
B
null is ignored
C
It throws NullPointerException
D
TreeSet converts null to an empty string

Question 8

What will be the output of the following code?

Java

import java.util.*;
public class Test {
    public static void main(String[] args) {
        Set<String> set = new LinkedHashSet<>();
        set.add("C");
        set.add("Java");
        set.add("Python");
        set.add("C");
        System.out.println(set);
    }
}

A
[C, Java, Python, C]
B
[Java, Python, C]
C
[C, Java, Python]
D
Compilation Error

Question 9

What is the main characteristic of the Set interface in Java?

A
Maintains insertion order
B
Does not allow duplicate elements
C
Allows duplicate elements
D
Stores elements in key-value pairs

Question 10

What is the default initial capacity of a HashSet in Java?

A
10
B
20
C
5
D
16

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