Inheritance
- What is the output of this program?
class N
{
int K;
void display()
{
System.out.println(K);
}
}
class M extends N
{
int L;
void display()
{
System.out.println(L);
}
}
public class inheritance_Example
{
public static void main(String args[])
{
M object = new M();
object.K=5;
object.L=6;
object.display();
}
}
-
View Hint View Answer Discuss in Forum
NA
Correct Option: E
Class N & class M both contain display() method, class M inherits class N, when display() method is called by object of class M, display() method of class M is executed rather than that of Class N.
- Which two classes use the Shape class correctly?
A. public class Circle implements Shape
{
private int radius;
}
B. public abstract class Circle extends Shape
{
private int radius;
}
C. public class Circle extends Shape
{
private int radius;
public void draw();
}
D. public abstract class Circle implements Shape
{
private int radius;
public void draw();
}
E. public class Circle extends Shape
{
private int radius;
public void draw()
{
/* code here */
}
}
F. public abstract class Circle implements Shape
{
private int radius;
public void draw()
{
/* code here */
}
}
-
View Hint View Answer Discuss in Forum
NA
Correct Option: D
If one is extending any class, then they should use extends keyword not implements.
- What is the output of this program?
class N
{
int K;
int L;
N()
{
K = 3;
L = 5;
}
}
public class Result
{
public static void main(String args[])
{
N obj1 = new N();
N obj2 = new N();
System.out.print(obj1.equals(obj2));
}
}
-
View Hint View Answer Discuss in Forum
NA
Correct Option: B
obj1 and obj2 are two different objects. equals() is a method of Object class, Since Object class is superclass of every class it is available to every object.
output:
- What is the output of this program?
final class n
{
int K;
}
class n1 extends n
{
int L;
System.out.println(L + " " + K);
}
public class inheritance_Example
{
public static void main(String args[])
{
n1 obj = new n1();
obj.display();
}
}
-
View Hint View Answer Discuss in Forum
NA
Correct Option: C
class n has been declared final hence it cannot be inherited by any other class. Hence class B does not have member i, giving compilation error.
Output: Compilation Error
- What is the output of this program?
class n
{
int K;
public void display()
{
System.out.println(K);
}
}
class m extends n
{
int L;
public void display()
{
System.out.println(L);
}
}
public class Dynamic_dispatch_Example
{
public static void main(String args[])
{
m obj2 = new m();
obj2.K = 3;
obj2.L = 5;
n r;
r = obj2;
r.display();
}
}
-
View Hint View Answer Discuss in Forum
NA
Correct Option: E
r is reference of type n, the program assigns a reference of object obj2 to r and uses that reference to call function display() of class m.
