Java Inheritance Quiz Practice Coding Questions

In this post, there are some 40 Java inheritance quiz type questions and answers which will help you to understand Java inheritance concept better.

Java Inheritance Quiz Practice Coding Questions :

1) Tinku has written the code like below. But, it is showing compile time error. Can you identify what mistake he has done?

class X
{
	//Class X Members
}

class Y
{
	//Class Y Members
}

class Z extends X, Y
{
	//Class Z Members
}

View Answer

Answer :
In Java, a class can not extend more than one class. Class Z is extending two classes – Class X and Class Y. It is a compile time error in Java.

2) What will be the output of this program?

class A
{
	int i = 10;
}

class B extends A
{
	int i = 20;
}

public class MainClass
{
	public static void main(String[] args)
	{
		A a = new B();

		System.out.println(a.i);
	}
}

View Answer

Answer :
10

3) What will be the output of the below program?

class A
{
	{
		System.out.println(1);
	}
}

class B extends A
{
	{
		System.out.println(2);
	}
}

class C extends B
{
	{
		System.out.println(3);
	}
}

public class MainClass
{
	public static void main(String[] args)
	{
		C c = new C();
	}
}

View Answer

Answer :
1
2
3

4) Can a class extend itself?

View Answer

Answer :
No. A class can not extend itself.

5) What will be the output of the following program?

class A
{
	String s = "Class A";
}

class B extends A
{
	String s = "Class B";

	{
		System.out.println(super.s);
	}
}

class C extends B
{
	String s = "Class C";

	{
		System.out.println(super.s);
	}
}

public class MainClass
{
	public static void main(String[] args)
	{
		C c = new C();

		System.out.println(c.s);
	}
}

View Answer

Answer :
Class A
Class B
Class C

6) What will be the output of this program?

class A
{
	static
	{
		System.out.println("THIRD");
	}
}

class B extends A
{
	static
	{
		System.out.println("SECOND");
	}
}

class C extends B
{
	static
	{
		System.out.println("FIRST");
	}
}

public class MainClass
{
	public static void main(String[] args)
	{
		C c = new C();
	}
}

View Answer

Answer :
THIRD
SECOND
FIRST

7) What will be the output of the below program?

class A
{
	public A()
	{
		System.out.println("Class A Constructor");
	}
}

class B extends A
{
	public B()
	{
		System.out.println("Class B Constructor");
	}
}

class C extends B
{
	public C()
	{
		System.out.println("Class C Constructor");
	}
}

public class MainClass
{
	public static void main(String[] args)
	{
		C c = new C();
	}
}

View Answer

Answer :
Class A Constructor
Class B Constructor
Class C Constructor

8) Private members of a class are inherited to sub class. True or false?

View Answer

Answer :
false. Private members are not inherited to sub class.

9) What will be the output of the following program?

class X
{
	static void staticMethod()
	{
		System.out.println("Class X");
	}
}

class Y extends X
{
	static void staticMethod()
	{
		System.out.println("Class Y");
	}
}

public class MainClass
{
	public static void main(String[] args)
	{
		Y.staticMethod();
	}
}

View Answer

Answer :
Class Y

10) Below code is showing compile time error. Can you suggest the corrections?

class X
{
	public X(int i)
	{
		System.out.println(1);
	}
}

class Y extends X
{
	public Y()
	{
		System.out.println(2);
	}
}

View Answer

Answer :
Write explicit calling statement to super class constructor in Class Y constructor.

class X
{
	public X(int i)
	{
		System.out.println(1);
	}
}

class Y extends X
{
	public Y()
	{
		super(10);          //Correction

		System.out.println(2);
	}
}

11) What is wrong with the below code? Why it is showing compile time error?

public class A
{
	public A()
	{
		System.out.println(1);

		super();

		System.out.println(2);
	}
}

View Answer

Answer :
Constructor calling statements ( super() or this() ), if written, must be the first statements in the constructor.Correct Code…

public class A
{
	public A()
	{
		super();         

		System.out.println(1);

		System.out.println(2);
	}
}

12) You know that compiler will keep super() calling statement implicitly as a first statement in every constructor. What happens if we write this() as a first statement in our constructor?

View Answer

Answer :
Compiler will not keep super() if you are writing this() as a first statement in your constructor.

13) Can you find out the error in the below code?

public class A
{
	public A(int i)
	{

	}
}

class B extends A
{

}

View Answer

Answer :
Class B doesn’t have any constructors written explicitly. So, compiler will keep default constructor. In that default constructor, there will be a calling statement to super class constructor (super()). But, it is undefined in Class A.To remove the errors, either define A() constructor in class A or write B() constructor in class B and call super class constructor explicitly.

public class A
{
	public A()
	{
		//Either keep this constructor
	}

	public A(int i)
	{

	}
}

class B extends A
{
	public B()
	{
		super(10);   //or else write this statement
	}
}

14) Which class is a default super class for every class in java?

View Answer

Answer :
java.lang.Object class

15) Can you find out the error in the below code?

public class A
{
	public A()
	{
		super();

		this(10);
	}

	public A(int i)
	{
		System.out.println(i);
	}
}

View Answer

Answer :
A constructor can have either super() or this() but not both.

16) What will be the output of this program?

class M
{
	static
	{
		System.out.println('A');
	}

	{
		System.out.println('B');
	}

	public M()
	{
		System.out.println('C');
	}
}

class N extends M
{
	static
	{
		System.out.println('D');
	}

	{
		System.out.println('E');
	}

	public N()
	{
		System.out.println('F');
	}
}

public class MainClass
{
	public static void main(String[] args)
	{
		N n = new N();
	}
}

View Answer

Answer :
A
D
B
C
E
F

17) What will be the output of the below program?

class M
{
	int i;

	public M(int i)
	{
		this.i = i--;
	}
}

class N extends M
{
	public N(int i)
	{
		super(++i);

		System.out.println(i);
	}
}

public class MainClass
{
	public static void main(String[] args)
	{
		N n = new N(26);
	}
}

View Answer

Answer :
27

18) What will be the output of the following program?

class M
{
	int i = 51;

	public M(int j)
	{
		System.out.println(i);

		this.i = j * 10;
	}
}

class N extends M
{
	public N(int j)
	{
		super(j);

		System.out.println(i);

		this.i = j * 20;
	}
}

public class MainClass
{
	public static void main(String[] args)
	{
		N n = new N(26);

		System.out.println(n.i);
	}
}

View Answer

Answer :
51
260
520

19) Why Line 10 in the below code is showing compilation error?

class X
{
	private int m = 48;
}

class Y extends X
{
	void methodOfY()
	{
		System.out.println(m);
	}
}

View Answer

Answer :
Because, private field ‘m’ is not visible to class Y.

20) What will be the output of the below program?

class X
{
	int m = 1111;

	{
		m = m++;

		System.out.println(m);
	}
}

class Y extends X
{
	{
		System.out.println(methodOfY());
	}

	int methodOfY()
	{
		return m-- + --m;
	}
}

public class MainClass
{
	public static void main(String[] args)
	{
		Y y = new Y();
	}
}

View Answer

Answer :
1111
2220

21) What will be the output of this program?

class A
{
	static String s = "AAA";

	static
	{
		s = s + "BBB";
	}

	{
		s = "AAABBB";
	}
}

class B extends A
{
	static
	{
		s = s + "BBBAAA";
	}

	{
		System.out.println(s);
	}
}

public class MainClass
{
	public static void main(String[] args)
	{
		B b = new B();
	}
}

View Answer

Answer :
AAABBB

22) What will be the output of the following program?

class X
{
	int i = 101010;

	public X()
	{
		i = i++ + i-- - i;
	}

	static int staticMethod(int i)
	{
		return --i;
	}
}

class Y extends X
{
	public Y()
	{
		System.out.println(staticMethod(i));
	}
}

public class MainClass
{
	public static void main(String[] args)
	{
		Y y = new Y();
	}
}

View Answer

Answer :
101010

23) What happens if both super class and sub class have a field with same name?

View Answer

Answer :
Super class field will be hidden in the sub class.

24) Does the below program execute successfully? If yes, what will be the output?

class A
{
	void A()
	{
		System.out.println(1);
	}
}

class B extends A
{
	void B()
	{
		A();
	}
}

public class MainClass
{
	public static void main(String[] args)
	{
		new B().B();
	}
}

View Answer

Answer :
Yes, but with a warning that method has a constructor name. Output will be
1

25) How do you prevent a field or a method of any class from inheriting to sub classes?

View Answer

Answer :
By declaring that particular field or method as private.

26) What will be the output of the below program?

class A
{
	int i = 1212;
}

class B extends A
{
	A a;

	public B(A a)
	{
		this.a = a;
	}
}

public class MainClass
{
	public static void main(String[] args)
	{
		A a = new A();

		B b = new B(a);

		System.out.println(a.i);

		System.out.println(b.i);

		System.out.println(b.a.i);

		b.a.i = 2121;

		System.out.println("--------");

		System.out.println(a.i);

		System.out.println(b.i);
	}
}

View Answer

Answer :
1212
1212
1212
——–
2121
1212

27) Does java support multiple inheritance?

View Answer

Answer :
Yes, but only through interfaces. Classes can implement more than one interfaces but can not extend more than one class.

28) What will be the output of this program?

class ClassOne
{
	 static int i, j = 191919;

	 {
		 --i;
	 }

	 {
		 j++;
	 }
}

public class ClassTwo extends ClassOne
{
	static
	{
		i++;
	}

	static
	{
		--j;
	}

	public static void main(String[] args)
	{
		System.out.println(i);

		System.out.println(j);
	}
}

View Answer

Answer :
1
191918

29) Does the fields with default visibility inherited to sub classes outside the package?

View Answer

Answer :
No. Fields with default access modifier are inherited to sub classes within the package.

30) Constructors are also inherited to sub classes. True or false?

View Answer

Answer :
false. Constructors, SIB and IIB are not inherited to sub classes. But, they are executed while instantiating a subclass.

31) What will be the output of the below program?

class A
{
	int[] a = new int[5];

	{
		a[0] = 10;
	}
}

public class MainClass extends A
{
	{
		a = new int[5];
	}

	{
		System.out.println(a[0]);
	}

	public static void main(String[] args)
	{
		MainClass main = new MainClass();
	}
}

View Answer

Answer :
0

32) What happens if both super class and sub class have a field with same name?

View Answer

Answer :
Super class field will be hidden in the sub class.

33) What will be the output of the below program?

class A
{
	int methodOfA(int i)
	{
		i /= 10;

		return i;
	}
}

class B extends A
{
	int methodOfB(int i)
	{
		i *= 20;

		return methodOfA(i);
	}
}

public class MainClass
{
	public static void main(String[] args)
	{
		B b = new B();

		System.out.println(b.methodOfB(100));
	}
}

View Answer

Answer :
200

34) What will be the outcome of the following program?

class A
{
	static int i;

	static
	{
		i++;
	}

	{
		++i;
	}
}

class B extends A
{
	static
	{
		--i;
	}

	{
		i--;
	}
}

public class MainClass
{
	public static void main(String[] args)
	{
		System.out.println(new B().i);
	}
}

View Answer

Answer :
0

35) Can a class be extended by more than one classes?

View Answer

Answer :
Yes, A class in java can be extended by multiple classes.

36) Does the below program written correctly? If yes, what will be the output?

public class MainClass
{
	public MainClass(int i, int j)
	{
		System.out.println(method(i, j));
	}

	int method(int i, int j)
	{
		return i++ + ++j;
	}

	public static void main(String[] args)
	{
		MainClass main = new MainClass(10, 20);
	}
}

View Answer

Answer :
Yes, class is written correctly. Output will be 31.

37) Does the below code prints “Hi….” on the console? If yes, how many times?

class X
{
	static
	{
		Y.methodOfY();
	}
}

class Y extends X
{
	static void methodOfY()
	{
		System.out.println("Hi....");
	}
}

public class MainClass
{
	public static void main(String[] args)
	{
		Y.methodOfY();
	}
}

View Answer

Answer :
Above code prints 2 times “Hi….” on the console.

38) What value the fields ‘i’ and ‘j’ will hold when you instantiate ‘ClassTwo’ in the below code?

class ClassOne
{
	static int i = 111;

	int j = 222;

	{
		i = i++ - ++j;
	}
}

class ClassTwo extends ClassOne
{
	{
		j = i-- + --j;
	}
}

View Answer

Answer :
i = -113
j = 110

39) When you instantiate a sub class, super class constructor will be also executed. True or False?

View Answer

Answer :
True

40) Does the below code written correctly? If yes, what will be the output?

class One
{
	int x = 2121;
}

class Two
{
	int x = 1212;

	{
		System.out.println(x);
	}
}

public class MainClass
{
	public static void main(String[] args)
	{
		Two two = new Two();
	}
}

View Answer

Answer :
Yes, above code is written correctly. Output will be 1212.

Also Read :

88 Comments

shiv darshan

December 17, 2015 / 4:34 pm Reply

Q 38 ) pls cross-verify the o/p of Q38.
class ClassOne
{
static int i = 111;

int j = 222;

{
i = i++ – ++j;
System.out.println(i);
}

}

class ClassTwo extends ClassOne
{

{
j = i– + –j;
System.out.println(j);
}
}

public class MainClass
{
public static void main(String[] args)
{
ClassTwo two = new ClassTwo();

}
}

o/p-
-112
110
- Divya
  
  March 9, 2016 / 8:06 am Reply
  
  Yes, I am also getting the same out put
  -112
  110
  - Ranger
    
    June 18, 2016 / 5:00 pm Reply
    
    in question 38, line number 15; that is
    j = i– + –j;
    
    value of “i” will get decremented from -112 to -113
    so the final value of i is -113
    - jothi
      
      November 26, 2019 / 8:11 pm Reply
      
      in question 38, line number 15; that is
      j = i– + –j;
      
      value of “i” will get same value 111(i-) + (-j) j value will get decremented 221
      so the final value is 332
  - Aamir
    
    October 25, 2016 / 8:04 am Reply
    
    class ClassOne
    {
    static int i = 111;
    int j = 222;
    {
    i = i++ – ++j; // i = 111(increment after instruction execution) – 223(increment before execution) => i = -112 , j =223
    }
    }
    class ClassTwo extends ClassOne
    {
    {
    j = i– + –j; => j = -112(decrement after execution) + 222(decrement before execution) => j = 110 && i gets decremented after execution => i = -112-1 = -113
    }
    } Hence i = -113, j=110 at the end
    - Mayank
      
      May 18, 2021 / 2:55 pm Reply
      
      its giving error: non-static variable j cannot be referenced from a static context
      System.out.println(“i: ” + i +”\n” + “j: ” + j);
      
      my code :
      class ClassOne
      {
      static int i = 111;
      
      int j = 222;
      
      {
      i = i++ – ++j;
      }
      }
      
      public class ClassTwo extends ClassOne
      {
      public static void main(String [] args) {
      System.out.println(“i: ” + i +”\n” + “j: ” + j);
      }
      
      {
      j = i– + –j;
      }
      
      }
      - Sagar Kori
        
        August 5, 2021 / 6:52 am
        
        i also gt sm otpt
      - Sagar Kori
        
        August 5, 2021 / 7:09 am
        
        variable j must be static
        static int j=222;
        then error will be removed
        but output same as given value
        output:111
        222
        becoz your all of instance block is not exicuted. it will be exicute during the class object creation.
        if you write this statenment in main method so all of instance block will exicute.
        ClassTwo obj1=new ClassTwo();
- Dhiraj Kumar
  
  February 1, 2017 / 6:16 am Reply
  
  print the value of i and j in main class
  then the output will be
  -113
  110
  - Eswari
    
    December 13, 2019 / 11:47 pm Reply
    
    how
- Coder
  
  January 9, 2018 / 3:26 pm Reply
  
  yes the output is wrong in the answer.
  - Aanchal Sharma
    
    June 26, 2019 / 4:05 am Reply
    
    yes,output is wrong.
    correct output is
    -112 for i
    110 for j
- Raunak Khandelwal
  
  April 22, 2020 / 11:01 am Reply
  
  For Q.38), output is right.
  Try it on any software like netbeans, or can use online compiler.
pri

February 2, 2016 / 8:27 pm Reply

I am Confused, please correct me.

I believe, Question number 2 is wrong. Because A a = new B() and a.i should be = 20.
- Divya
  
  March 8, 2016 / 2:20 pm Reply
  
  Hi pri,
  It points to the type of the reference it is referred to, not the type of the reference it is assigned.
  
  In case of overriding of method, it is reverse and it is so called Runtime Method Dispatch
  - ash
    
    April 12, 2016 / 12:44 am Reply
    
    hello divya can you please elaborate?
    
    for eg. what would be the output in the following?
    
    lass Animal{
    
    public void move(){
    System.out.println(“Animals can move”);
    }
    }
    
    class Dog extends Animal{
    
    public void move(){
    System.out.println(“Dogs can walk and run”);
    }
    }
    
    public class TestDog{
    
    public static void main(String args[]){
    Animal a = new Animal(); // Animal reference and object
    Animal b = new Dog(); // Animal reference but Dog object
    
    a.move();// runs the method in Animal class
    
    b.move();//Runs the method in Dog class
    
    For me, both seems the same. Please enlighten me on this !!!
    - Vishal
      
      July 19, 2016 / 11:02 am Reply
      
      Hello Ash,
      the example u gave was of Run-time polymorphism, when u give reference of subclass to parent class variable and are calling the subclass method by the reference variable of Parent class. Since it refers to the subclass object and subclass method overrides the Parent class method, subclass method is invoked at runtime.
      
      and in question no. 2 he is trying to do the same but Method is overridden not the datamembers, so runtime polymorphism can’t be achieved by data members. Since you are accessing the datamember which is not overridden, hence it will access the datamember of Parent class always.
    - Begede Silvester A
      
      October 27, 2016 / 2:24 am Reply
      
      animals can move
      dogs can walk and run
  - Kundan
    
    January 7, 2017 / 3:57 pm Reply
    
    Hi pri
    This is variable not method variable not comes under overriding so its work as a overloading
- ai
  
  June 22, 2016 / 2:51 pm Reply
  
  I got the same view on it
- gyan pr
  
  September 3, 2017 / 2:10 pm Reply
  
  i also think so.
- beginer
  
  May 29, 2018 / 10:27 am Reply
  
  the answer is true b/c it is a rule in java when is being created then control goes through parent class if it exist
- Rajdeep Patil
  
  April 22, 2022 / 11:40 pm Reply
  
  Variables cannot be overloaded bro…
shashi

March 26, 2016 / 12:08 pm Reply

in 28 question i value not declared but it becomes 1 how is it
- Abhijeet
  
  June 7, 2016 / 8:50 am Reply
  
  i is initialized to 0 in Parent Class and Child Class can access it has default access specifier.
  Execution Flow:
  All static blocks are executed, since there are no constructor’s initializer blocks are not executed.
Ranger

June 18, 2016 / 2:59 pm Reply

please explain the line number 6 of question 20
m = m++;
- gurpreet
  
  December 29, 2016 / 5:57 am Reply
  
  There is a solution my friend
  
  M=1111 is initialized .
  
  When compiler goes to the statement
  
  M=m++; then the processing of code is
  Firstly m++ is a post increament value so it follows first use then change so without changing to1112 it assigns 1111 to M.
  
  Thats y we r getting output 1111.
  
  if you compile only m++ and not assigning this m++ to M then definitely u will get 1112.
  
  hope it helps you.
hari

August 15, 2016 / 6:58 pm Reply

Q 26) Can enay explain below
b.a.i = 2121;

System.out.println(“——–“);

System.out.println(a.i);

System.out.println(b.i);

Output:
———-
——–
2121
1212
- Chris
  
  March 5, 2018 / 2:26 am Reply
  
  Yes, b’s reference to (A a) actually points to the ‘a’ that was instantiated with this statement A a = new A();.
  This statement B b = new B(a); Notice the ‘a’ as an argument to the constructor. b’s b.a actually points to ‘a’. So b.a.i changes a’s int i.
lol

September 8, 2016 / 10:41 am Reply

can u explain question no 5
Shruti Sharma

October 5, 2016 / 3:50 pm Reply

can u plzz explain 20 question
- yenesew
  
  December 25, 2016 / 5:36 pm Reply
  
  are u say Q20# or total 1-20 questions?
Nirajan Thapa

February 8, 2017 / 8:30 pm Reply

class A
{
int i = 10;
}

class B extends A
{
int i = 20;
}

public class MainClass
{
public static void main(String[] args)
{
A a = new B();

System.out.println(a.i);
}
}

This calls the parent class variable. But

class A {
int i = 10;

public void print() {
System.out.println(“class A”);
}
}

class B extends A {
int i = 20;

public void print() {
System.out.println(“class B”);
}
}

public class MainClass {
public static void main(String[] args) {
A a = new B();
a.print();

}
}

It calls the child method. Its like same inheritance. Can anybody tell me how is this?
- Shikha Pareta
  
  June 8, 2017 / 4:55 am Reply
  
  class A
  {
  int i = 10;
  }
  
  class B extends A
  {
  int i = 20;
  }
  
  public class MainClass
  {
  public static void main(String[] args)
  {
  A a = new B();
  
  System.out.println(a.i);
  }
  }
  
  This calls the parent class variable. But
  
  class A {
  int i = 10;
  
  public void print() {
  System.out.println(“class A”);
  }
  }
  
  class B extends A {
  int i = 20;
  
  public void print() {
  System.out.println(“class B”);
  }
  }
  
  public class MainClass {
  public static void main(String[] args) {
  A a = new B();
  a.print();
  
  }
  }
  
  In this case method call is based on actual reference type.And here in this case you are passing the reference of parent class.Where as in another question your are orerriding the print method in its sub-class in that case method cal l is based on actual object passed to it.
sonam

February 9, 2017 / 2:46 pm Reply

why output is 10 instead of 20?
class A
{
int i = 10;
}

class B extends A
{
int i = 20;
}

public class MainClass
{
public static void main(String[] args)
{
A a = new B();

System.out.println(a.i);
}
}
- Ajay
  
  November 29, 2017 / 11:03 pm Reply
  
  Its because when you override a variable it creates separate copy of the variable, one corresponds to superclass , the other one for subclass. So here, a is a superclass reference of the object of type B. So it’s referring to the A portion of the variable.
- Aryan
  
  June 7, 2018 / 6:59 pm Reply
  
  here the output is 10 instead of 20 because during time of overriding non static data member create their own distinct copy,
JYOTI UMARJI

February 14, 2017 / 8:53 pm Reply

class A
{
String s = “Class A”;
}

class B extends A
{
String s = “Class B”;

{
System.out.println(super.s);
}
}

class C extends B
{
String s = “Class C”;

{
System.out.println(super.s);
}
}

public class MainClass
{
public static void main(String[] args)
{
C c = new C();

System.out.println(c.s);
}
}
View Answer
Answer :
Class A
Class B
Class C
according to me output is
class C
class b
class a
please explain why it’s reverse.
- Swagata
  
  April 3, 2017 / 10:22 am Reply
  
  First of all, initialization block is been put inside constructor by compiler. Here default constructor is used by compiler. C c = new C(); –> here C() constructor is called & by default , compiler will call super constructor which is B(), but there is no constructor mentioned, it will call again default constructor for B class & as I said it will put initialization block inside constructor.
  So System.out.println(super.s); of class B will be executed first, (super.s) is “Class A”. After this System.out.println(super.s); of class C will be executed so “Class B” will be print Then System.out.println(c.s);–> “Class C”
srashti

March 17, 2017 / 7:49 am Reply

class X
{
int m = 1111;

{
m = m++;

System.out.println(m);
}
}

class Y extends X
{
{
System.out.println(methodOfY());
}

int methodOfY()
{
return m– + –m;
}
}

public class MainClass
{
public static void main(String[] args)
{
Y y = new Y();
}
}
nav

March 25, 2017 / 6:39 am Reply

30) Constructors are also inherited to sub classes. True or false?
Answer : false. Constructors, SIB and IIB are not inherited to sub classes. But, they are executed while instantiating a subclass.

but on question 28) the code is executing without instantiating the class, means SIB is executing and giving output. anyone plz explain me more on this.
- Manihas
  
  August 3, 2017 / 12:33 am Reply
  
  SIBs are executed during class loading i.e., when a .class file is loaded but before even a class is instantiated(or not instantiated) during execution time. So in any program all the static blocks will be executed even if an instance is created or not.
sagi

March 28, 2017 / 9:43 am Reply

Excellent stuff good for java people.
- Palak
  
  June 10, 2017 / 4:19 pm Reply
  
  Question 10)
  
  I thought super class constructor will be call automatically.
  why it is added super(10).
abhi

June 10, 2017 / 7:28 pm Reply

Can a class be extended by more than one classes?
ans is NO
question no 35 is wrong answer because multiple inheritance not support in java
- Manihas
  
  August 3, 2017 / 12:41 am Reply
  
  class A {
  ……
  }
  class B extends A{
  ……..
  }
  class C extends A{
  ………….
  }
  The above code is what the question interprets, that means A can be a parent class for any number of classes. This is example for hierarchical Inheritance.
  
  On the other hand multiple inheritance means a class extending more than one class at the same time i.e.,
  For example: class A extends B,C
  which creates ambiguity.
  
  class A{
  void msg(){System.out.println(“Hello”);}
  }
  class B{
  void msg(){System.out.println(“Welcome”);}
  }
  class C extends A,B{//suppose if it were
  
  Public Static void main(String args[]){
     C obj=new C();
     obj.msg();//Now which msg() method would be invoked?
  }
  }
  
  O/p: Compile time error
  - Jambu Balaraman
    
    May 13, 2018 / 10:31 am Reply
    
    The object is created for class C but msg() is not overridden. so compiler throws an error.
- sai Teja
  
  April 24, 2019 / 2:16 am Reply
  
  no , i think you misunderstand the question,question is “can we use base /parent/super class in more than one class its a hierarical inheritance
  |—-c2
  |—-c3
  c1—-> |—-c4
  |—-c5
- Amit Gupta
  
  June 10, 2019 / 6:33 pm Reply
  
  Can anybody explain me the qstn number 16….as well as qstn 20 output is why 2220 why not 2221……
  
  class M
  {
  static
  {
  System.out.println(‘A’);
  }
  
  {
  System.out.println(‘B’);
  }
  
  public M()
  {
  System.out.println(‘C’);
  }
  }
  
  class N extends M
  {
  static
  {
  System.out.println(‘D’);
  }
  
  {
  System.out.println(‘E’);
  }
  
  public N()
  {
  System.out.println(‘F’);
  }
  }
  
  public class MainClass
  {
  public static void main(String[] args)
  {
  N n = new N();
  }
  }
Aaina

June 27, 2017 / 7:09 am Reply

can anyone explain question no. 16?
Kapil Baraskar

July 10, 2017 / 3:45 am Reply

Please Explain Q 18 ?
- Manihas
  
  August 3, 2017 / 12:59 am Reply
  
  public N(int j)
      {
          super(j);
  
          System.out.println(i);
  
          this.i = j * 20;
  
  When the above code starts executing as a per the Statement;
  N n = new N(26);
  At this point of time, super(j); will point the execution to
  
  public M(int j)
      {
          System.out.println(i);
  
          this.i = j * 10;
  }
  
  And ‘i’ will be printed which is 51 at that time, then the instance variable ‘i’ will change since its value as per
  this.i = j * 10;
  where j is 26, which makes the value of i as 260.
  
  So the o/p so far is
  51
  
  Now the execution is handed back to the constructor in the child class N constructor as shown below:
  public N(int j)
      {
          super(j);
          System.out.println(i);
          this.i = j * 20;}
  Now value of i at this instance(i.e., 260) is printed.
  
  Next
  this.i = j * 20;
  is executed and the value of i now is 520.
  
  which is printed when the print statement in the main() method is executed.
Nisha S

August 11, 2017 / 7:04 am Reply

in a file the classes like class A and class B are inherited and they are public. And even the main Class also public, then in what name the file should be saved.
import java.io.*;
public class A
{
int i = 10;
}

public class B extends A
{
int i = 20;
}

public class MainClass
{
public static void main(String[] args)
{
A a = new B();

System.out.println(a.i);
}
}
durgendra

August 23, 2017 / 8:53 am Reply

Question 17 has compile time error because super class don’t have default constructor.
Rahul Kumar

August 26, 2017 / 5:32 am Reply

Can anyone explain the reason of question no-2

class A
{
int i = 10;
}

class B extends A
{
int i = 20;
}

public class MainClass
{
public static void main(String[] args)
{
A a = new B();

System.out.println(a.i);
}
}
- Hanadi
  
  September 27, 2017 / 6:42 pm Reply
  
  The object a is declared as type A but it will not be aware of the variable i in class B.
  if you try to change the declaration as
  B a = new B();
  Then you will get 20.
M LTirupathi Reddy

September 10, 2017 / 9:38 am Reply

Can anyone explain the following code in Q.No-26
System.out.println(b.a.i);

b.a.i = 2121;

System.out.println(“——–“);

System.out.println(a.i);

System.out.println(b.i);
- Chris
  
  March 5, 2018 / 2:55 am Reply
  
  Yes, b’s reference to (A a) actually points to the ‘a’ that was instantiated with this statement A a = new A();.
  This statement B b = new B(a); Notice the ‘a’ as an argument to the constructor. b’s b.a actually points to ‘a’. So b.a.i changes a’s int i.
  - Shubham Sharma
    
    September 4, 2019 / 4:01 pm Reply
    
    is call by value, call by reference applicable here, or is it part of c++ only?
sagar

September 12, 2017 / 6:07 pm Reply

Hi Rahul,
A a = new B(); this is called casting. This statement tells Child class (B) referencing to parent class (A), so parent class instance varible will be printed. If this code is replaced with
B b = new B();
System.out.println(b.i); // you can see “20” output. here child class instance is referncing to child class variable.
Jahangeer

November 10, 2017 / 5:22 pm Reply

To admin
Answer of Q#2 is wrong .You should correct it. Its correct answer is 20
- rahul
  
  January 4, 2018 / 12:19 pm Reply
  
  Answer 10 is correct, overriden is applied only method not on instance variable.
Chaudhary Habib

November 22, 2017 / 8:05 am Reply

I also thinks it should be 20.
sneh

November 23, 2017 / 5:48 pm Reply

can anyone explain ques 26
farookh shaik

November 28, 2017 / 6:22 am Reply

Q10) can you please explain the flow of execution
ram

November 28, 2017 / 7:43 am Reply

please help explaining 20 detail
vasu

December 16, 2017 / 11:00 am Reply

please explain q32
kareem syed

January 7, 2018 / 6:44 pm Reply

please modify the code for Question 1 to make it runnable
Abhinay

January 28, 2018 / 11:00 am Reply

I have a query regarding question number 12. As you said “Compiler will not keep super() if you are writing this() as a first statement in your constructor.” Please refer blow code and output
public class Test {

public static void main(String[] args) {
Y y = new Y(10);
}
}

class X
{
X(){
System.out.println(“X class”);
}
}

class Y extends X
{
Y(){
System.out.println(“Y class”);
}

Y(int i){
this();
System.out.println(“Y class : “+ i);
}
}

Actual Output :
X class
Y class
Y class : 10

Expected output :
Y class
Y class : 10

So conclusion is “Compiler will always keep super() whether we are writing this() or not as a first statement in your constructor.”
Please correct me if I did anything wrong.
Somesh Gangwar

March 5, 2018 / 12:35 pm Reply

Anyone explain question 28.
How the value of i will become 1.
P Pravin

March 8, 2018 / 11:16 am Reply

Thanks, brother. Nice Article, Great work…!?
hari

April 5, 2018 / 3:07 pm Reply

class A
{
public A(){
System.out.println(” A”);
}
static
{
System.out.println(“THIRD”);
}
}

class B extends A
{

public B(){
System.out.println(“B”);
}
static
{
System.out.println(“SECOND”);
}
}

class C extends B
{
static
{
System.out.println(“FIRST”);
}

public C(){
System.out.println(“C”);
}
}

public class MainClass
{
public static void main(String[] args)
{
A c = new C();
}
}
Vinay

April 11, 2018 / 5:43 am Reply

Q no 9: Why output is Class Y and why not it is :
Class X
Class Y
Simmi

April 27, 2018 / 4:22 pm Reply

Please explain Q20.
liza

May 2, 2018 / 4:53 pm Reply

Q 21 class A
{
static String s = “AAA”;

static
{
s = s + “BBB”;
}

{
s = “AAABBB”;
}
}

class B extends A
{
static
{
s = s + “BBBAAA”;
}

{
System.out.println(s);
}
}

public class MainClass
{
public static void main(String[] args)
{
B b = new B();
}

how is answer AAABBB . shouldn’t be AAABBBBBBAAA .
- liza
  
  May 2, 2018 / 5:00 pm Reply
  
  When the Object is created B b = new B() ; it calls the default constructor in B which in turns calls the default constructor of A .. where s = AAA , static function of A is executed which makes s as AAABBB then IIB is executed which makes s = AAABBB, then control goes back to Class B where SIB is executed where s = s + “BBBAAA” which makes s as AAABBBBBBAAA and then IIB is executed which prints AAABBBBBBAAA ? Isn’t it correct . Please explain .
- zvikiNozadze
  
  June 30, 2019 / 12:26 am Reply
  
  Q 21 ) first static methods are executed then non-static so s will get “AAABBBBBBAAA” and then s = “AAABBB” will and then print statement.
Siddarth Mishra

May 11, 2018 / 2:49 pm Reply

for Q20 output is as follows:
1112
2222
- Hugo Martinez
  
  June 8, 2018 / 11:20 pm Reply
  
  you are not taking into consideration the decrement and assignment rules for “–“:
  
  i = m–; // the value of m is decreased after m is assigned to i, so “i” doesn’t change: i = 1111 and m=1110
  j= –m; // the value of m is decreased before m is assigned to j, so m = 1110 – 1 = 1109 and then the result will be assigned to j, j = 1109
  z = i + j; // thus z = 1111 + 1109 = 2220
Radha Kireeti

June 6, 2018 / 1:08 am Reply

Could anyone please explain the execution flow of the program given in Q16?
Krishna Prasad

September 21, 2018 / 2:37 pm Reply

it’s a nice code
asmit lade

October 29, 2018 / 2:44 pm Reply

plz explain Question 26 I don’t understand what is b.a.i
Gurubux

December 15, 2018 / 12:58 pm Reply

Answer of Q31 is 0
Aradhana

December 25, 2018 / 4:21 pm Reply

Please explain question. 16 I didn’t understand the order of execution.
- Shaik jakeer hussain
  
  August 25, 2019 / 4:42 pm Reply
  
  class M
  {
  static
  {
  System.out.println(‘A’);
  }
  
  {
  System.out.println(‘B’);
  }
  
  public M()
  {
  System.out.println(‘C’);
  }
  }
  
  class N extends M
  {
  static
  {
  System.out.println(‘D’);
  }
  
  {
  System.out.println(‘E’);
  }
  
  public N()
  {
  System.out.println(‘F’);
  }
  }
  
  public class MainClass
  {
  public static void main(String[] args)
  {
  N n = new N();
  }
  }
  //output : A
  D
  B
  C
  E
  F
  
  ==> We know that static block will be execute before the main ( So A & D will be printed at the top )
  ==> Now the child class created an object for its own class and its constructor get invoked
  A child class constructor has super class as default so parent class constructor invoked and prints B & C, later child class constructors get printed E & F
Lizara

August 13, 2019 / 8:13 pm Reply

Hi
Can i have an explanation for number 5 , my answer was Class A only and yet also B and C are printed
sonali

May 29, 2021 / 5:08 pm Reply

class A
{
{
System.out.println(1);
}
}

class B extends A
{
{
System.out.println(2);
}
}

class C extends B
{
{
System.out.println(3);
}
}

public class MainClass
{
public static void main(String[] args)
{
C c = new C();
}
}

Can someone explain why its printing 1 2 3?
Mayank Chopra

May 30, 2021 / 12:26 pm Reply

the order of excution in java is
static block
instance block
constructor
and any function that is called by an object
instance block example
{
//some code
} above block is called instance block

after C class object declaration there is call to its base class that is B and B is also inherited that is derived class if A so class A is called and the first thing is be executed is static block but there is no static block so instance block is executed of class A, B, C respectively in same order as
1
2
3

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