Java Arrays, Strings & Collections MCQs | Beginner to Advanced

1.What is the index of the first element in a Java array?

a) 1
b) 0
c) -1
d) Depends on array size

2. Which of the following is used to declare an array in Java?

a) int arr;
b) int arr[];
c) array int arr;
d) arr int[];

3. What will be the output?

int[] arr = {1, 2, 3};
System.out.println(arr.length);

a) 2
b) 3
c) 1
d) Error

4. Which method is used to compare two strings in Java?

a) ==
b) compare()
c) equals()
d) match()

5. What is the output?

String s = "Java";

System.out.println(s.charAt(2)); 

a) J
b) a
c) v
d) Error

6. Strings in Java are:

a) Mutable
b) Immutable
c) Dynamic
d) Static

7. Which class is used to create a dynamic array in Java?

a) HashMap
b) ArrayList
c) HashSet
d) TreeMap

8. Which method adds an element to an ArrayList?

a) insert()
b) add()
c) put()
d) push()

9. What is the default size of an ArrayList?

a) 5
b) 8
c) 10
d) 15

10. Which collection does NOT allow duplicate elements?

a) ArrayList
b) HashMap
c) HashSet
d) LinkedList

11. Which method is used to get a value from a HashMap?

a) fetch()
b) get()
c) retrieve()
d) value()

12. What will happen if you add duplicate keys in a HashMap?

a) Error occurs
b) Duplicate stored
c) Old value replaced
d) Program crashes

13. Which of the following allows key-value pairs?

a) ArrayList
b) HashSet
c) HashMap
d) Stack

14. What is the output?

String s1 = "Hello";

String s2 = "Hello";

System.out.println(s1 == s2);

a) true
b) false
c) Error
d) Depends

15. Which method returns the size of a collection?

a) length()
b) size()
c) count()
d) getSize()

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