Java Questions & Answers – Java.util – Array Class

This section of our 1000+ Java MCQs focuses on Array class under java.util library of Java Programming Language.

1. Which of these standard collection classes implements all the standard functions on list data structure?
a) Array
b) LinkedList
c) HashSet
d) AbstractSet
View Answer

Answer: a
Explanation: None.

2. Which of these classes implements Set interface?
a) ArrayList
b) HashSet
c) LinkedList
d) DynamicList
View Answer

Answer: b
Explanation: HashSet and TreeSet implements Set interface where as LinkedList and ArrayList implements List interface.

3. Which of these method is used to make all elements of an equal to specified value?
a) add()
b) fill()
c) all()
d) set()
View Answer

Answer: b
Explanation: fill() method assigns a value to all the elements in an array, in other words it fills the array with specified value.

4. Which of these method of Array class is used sort an array or its subset?
a) binarysort()
b) bubblesort()
c) sort()
d) insert()
View Answer

Answer: c
Explanation: None.

5. Which of these methods can be used to search an element in a list?
a) find()
b) sort()
c) get()
d) binaryserach()
View Answer

Answer: d
Explanation: binaryserach() method uses binary search to find a specified value. This method must be applied to sorted arrays.

6. Which of these method is used to change an element in a LinkedList Object?
a) change()
b) set()
c) redo()
d) add()
View Answer

Answer: c
Explanation: An element in a LinkedList object can be changed by first using get() to obtain the index or location of that object and the passing that location to method set() along with its new value.

7. What is the output of this program?

  1.     import java.util.*;
  2.     class Arraylist {
  3.         public static void main(String args[]) {
  4.             ArrayList obj1 = new ArrayList();
  5.             ArrayList obj2 = new ArrayList();
  6.             obj1.add("A");
  7.             obj1.add("B");
  8.             obj2.add("A");
  9.             obj2.add(1, "B");
  10.             System.out.println(obj1.equals(obj2));
  11.         }
  12.     }

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

Answer: c
Explanation: obj1 and obj2 are an object of class ArrayList hence it is a dynamic array which can increase and decrease its size. obj.add(“X”) adds to the array element X and obj.add(1,”X”) adds element x at index position 1 in the list, Both the objects obj1 and obj2 contain same elements i:e A & B thus obj1.equals(obj2) method returns true.
Output:
$ javac Arraylist.java
$ java Arraylist
true

8. 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.sort(array);
  8.             for (int i = 0; i < 5; ++i)
  9.             	System.out.print(array[i]);;
  10.         }
  11.     }

a) 12345
b) 54321
c) 1234
d) 5432
View Answer

Answer: b
Explanation: Arrays.sort(array) method sorts the array into 1,2,3,4,5.
Output:
$ javac Array.java
$ java Array
12345

9. 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
View Answer

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.
Output:
$ javac Array.java
$ java Array
58881

10. 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.sort(array);
  8.             System.out.print(Arrays.binarySearch(array, 4));
  9.         }
  10.     }

a) 2
b) 3
c) 4
d) 5
View Answer

Answer: b
Explanation: None.
Output:
$ javac Array.java
$ java Array
3

Sanfoundry Global Education & Learning Series – Java Programming Language.

About

Manish Bhojasia, a technology veteran with 17+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer and SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage & Cluster Administration, Advanced C Programming, SAN Storage Technologies, SCSI Internals and Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him below.


Sanfoundry Training Center of Excellence (CoE)

Manish Bhojasia, a technology veteran with 17+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer and SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage & Cluster Administration, Advanced C Programming, SAN Storage Technologies, SCSI Internals and Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him below.







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