Java Questions & Answers – Collection Framework Overview

This section of our 1000+ Java MCQs focuses on collection framework of Java Programming Language.

1. Which of these packages contain all the collection classes?
a) java.lang
b) java.util
c) java.net
d) java.awt
View Answer

Answer: b
Explanation: None.

2. Which of these classes is not part of Java’s collection framework?
a) Maps
b) Array
c) Stack
d) Queue
View Answer

Answer: d
Explanation: Queue is not a part of collection framework.

3. Which of these interface is not a part of Java’s collection framework?
a) List
b) Set
c) SortedMap
d) SortedList
View Answer

Answer: d
Explanation: SortedList is not a part of collection framework.

4. Which of these methods deletes all the elements from invoking collection?
a) clear()
b) reset()
c) delete()
d) refresh()
View Answer

Answer: a
Explanation: clear() method removes all the elements from invoking collection.

5. What is Collection in Java?
a) A group of objects
b) A group of classes
c) A group of interfaces
d) None of the mentioned
View Answer

Answer: a
Explanation: A collection is a group of objects, it is similar to String Template Library (STL) of C++ programming language.

6. 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

7. What is the output of this program?

  1.     import java.util.*;
  2.     class vector {
  3.         public static void main(String args[]) {
  4.             Vector obj = new Vector(4,2);
  5.             obj.addElement(new Integer(3));
  6.             obj.addElement(new Integer(2));
  7.             obj.addElement(new Integer(5));
  8.             obj.removeAll(obj);
  9.             System.out.println(obj.isEmpty());
  10.         }
  11.     }

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

Answer: c
Explanation: firstly elements 3, 2, 5 are entered in the vector obj, but when obj.removeAll(obj); is executed all the elements are deleted and vector is empty, hence obj.isEmpty() returns true.
Output:
$ javac vector.java
$ java vector
true

8. What is the output of this program?

  1.     import java.util.*;
  2.     class stack {
  3.         public static void main(String args[]) {
  4.             Stack obj = new Stack();
  5.             obj.push(new Integer(3));
  6.             obj.push(new Integer(2));
  7.             obj.pop();
  8.             obj.push(new Integer(5));
  9.      	    System.out.println(obj);
  10.         }
  11.     }

a) [3, 5]
b) [3, 2]
c) [3, 2, 5]
d) [3, 5, 2]
View Answer

Answer: a
Explanation: push() and pop() are standard functions of the class stack, push() inserts in the stack and pop removes from the stack. 3 & 2 are inserted using push() the pop() is used which removes 2 from the stack then again push is used to insert 5 hence stack contains elements 3 & 5.
Output:
$ javac stack.java
$ java stack
[3, 5]

9. What is the output of this program?

  1.     import java.util.*;
  2.     class hashtable {
  3.         public static void main(String args[]) {
  4.             Hashtable obj = new Hashtable();
  5.             obj.put("A", new Integer(3));
  6.             obj.put("B", new Integer(2));
  7.             obj.put("C", new Integer(8));
  8.             obj.remove(new String("A"));
  9.             System.out.print(obj);
  10.         }
  11.     }

a) {C=8, B=2}
b) [C=8, B=2]
c) {A=3, C=8, B=2}
d) [A=3, C=8, B=2]
View Answer

Answer: b
Explanation: None.
Output:
$ javac hashtable.java
$ java hashtable
{C=8, B=2}

10. What is the output of this program?

  1.     import java.util.*;
  2.     class Bitset {
  3.         public static void main(String args[]) {
  4.             BitSet obj = new BitSet(5);
  5.             for (int i = 0; i < 5; ++i)
  6.                 obj.set(i);
  7.             obj.clear(2);
  8.             System.out.print(obj);
  9.         }
  10.     }

a) {0, 1, 3, 4}
b) {0, 1, 2, 4}
c) {0, 1, 2, 3, 4}
d) {0, 0, 0, 3, 4}
View Answer

Answer: a
Explanation: None.
Output:
$ javac Bitset.java
$ java Bitset
{0, 1, 3, 4}

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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.

1000 Java MCQs | Quiz

Integer and Floating Data Types
Character and Boolean Data Types
Literals & Variables
Type Conversions, Promotions and Castings
Arrays
Arithmetic Operators
Bitwise Operators
Relational Operators and Boolean Logic Operators
Assignment Operators and Operator Precedence
Control Statements
Class Fundamentals & Declaring objects
Introduction to Methods
Constructors & Garbage Collection
Overloading Methods & Argument Passing
Access Control
Arrays Revisited & Keyword static
String Class
Inheritance
Method overriding
The Object Class
String Handling Basics
Character Extraction
String Comparison
Searching & Modifying a String
StringBuffer class
StringBuffer Methods
Packages
Interfaces
Java.lang Introduction
Java.lang - Integer, Long And Character Wrappers
Java.lang - Void, Process and System Class
Java.lang - Object & Math Class
Java.io Introduction
Java.io Byte Streams
Java.io Character Streams
Serialization
Serialization & Deserialization
Networking Basics
URL class
HttpResponse & URLConnection Class
networking - Server, Sockets & httpd Class
networking - httpd.java Class
networking - Datagrams
Java.util - ArrayList Class
Java.util - LinkedList, HashSet & TreeSet Class
Java.util - Maps
Java.util - Array Class
Java.util - Vectors & Stack
Java.util - Dictionary, Hashtable & Properties
Java.util - BitSet & Date class
Methods Taking Parameters
Exceptional Handling Basics
Exceptions Types
Throw, Throws & Nested Try
isAlive(), Join() & Thread Synchronization
Implementing Runnable interface for Threads
Thread class
Multithreading Basics
Networking Basics
Finally & Built in Exceptions
Creating Threads
Input & Output Basics
Reading Console Input
Writing Console Output
Reading & Writing Files
Applets Fundamentals
Core Java API Packages
Remote Method Invocation (RMI)
Text Formatting
Event Handling Basics
ActionEvent & AdjustmentEvent Class
ComponentEvent, ContainerEvent & FocusEvent Class
MouseEvent, TextEvent & WindowEvent Class
Event Listeners Interfaces
Java.lang - Rounding Functions
Java.lang - Miscellaneous Math Methods & StrictMath Class
Java.lang - ThreadGroup class & Runnable Interface
Java.lang - System Class Advance
Java.lang - Double & Float Wrappers
Java.lang - Byte & Short Wrappers
Java.lang - Character Wrapper Advance
Java.lang - Boolean Wrapper Advance
Java.lang - Runtime & ClassLoader Classes
java.lang - Class
Collection Framework Overview
Collections Interface
Collection Algorithms
Iterators
Locale & Random Classes
Observable & Timer Class
Restrictions On Generics
Wildcards
Recursion
Command Line Arguments
Inheritance - Abstract Class and Super
Try & Catch
Creating Exceptions
Generics
Generic Methods
Type Interface
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