Unit-3 Practice Programs-5.docx

1. A program that demonstrates the extends keyword in Java is given as
follows
Code:
class A {
int a = 9;
}
class B extends A {
int b = 4;
}
public class Demo {
public static void main(String args[]) {
B obj = new B();
System.out.println("Value of a is: " + obj.a);
System.out.println("Value of b is: " + obj.b);
}
}
Output: Value of a is: 9
Value of b is: 4
Practice Program-2 on Extend Keyword
class Animal {
// fields of the parent class
String name;
String sound;
int noOfLegs;
// default constructor of the parent class
public Animal (){}
// parameterized constructor of the parent class
public Animal (String name, String sound, int legs){
this.name = name;
this.sound = sound;
this.noOfLegs = legs;

}
// method of the parent class
public void display() {
System.out.println("My name is " + name);
System.out.println("My sound is " + sound);
System.out.println("My no. of legs is " + noOfLegs);
}
}
// inherit from Animal
class Dog extends Animal {
String color;
String breed;
// new method in subclass
public Dog(String name, String sound ,int legs, String
color, String breed){
super(name,sound,legs);
this.color = color;
this.breed = breed;
}
public void display() {
super.display();
System.out.println("My color is " + color);
System.out.println("My breed is " + breed);
}
}
public class Main {
public static void main(String[] args) {
// create an object of the subclass
Dog dog1 = new
Dog("Billy","Bark",4,"Brown","Labrador");
dog1.display();
System.out.println("------------------");
Dog dog2 = new Dog("Grace","Bark",4,"Black","Husky");

dog2.display();
System.out.println("------------------");
Dog dog3 = new Dog("Hugo","Bark",4,"Gray","Poodle");
dog3.display();
}
}
Output:
My name is Billy
My sound is Bark
My no. of legs is 4
My color is Brown
My breed is Labrador
------------------
My name is Grace
My sound is Bark
My no. of legs is 4
My color is Black
My breed is Husky
------------------
My name is Hugo
My sound is Bark
My no. of legs is 4
My color is Gray
My breed is Poodle

Program 3. Demonstrate execution of constructor in Single inheritance
/* Parent Class */
class ParentClass
{
/* Constructor */
ParentClass()
{
System.out.println("ParentClass constructor executed.");
}
}
/* Child Class */
class ChildClass extends ParentClass
{
/* Constructor */
ChildClass()
{
System.out.println("ChildClass constructor executed.");
}
}
public class OrderofExecution1
{
/* Driver Code */
public static void main(String ar[])
{
/* Create instance of ChildClass */
System.out.println("Order of constructor execution...");
new ChildClass();
}
}

Order of constructor execution...
ParentClass constructor executed.
ChildClass constructor executed.
Program 4. Demonstrate execution of constructor in multiple inheritances
class College
{
/* Constructor */
College()
{
System.out.println("College constructor executed");
}
}
class Department extends College
{
/* Constructor */
Department()
{
System.out.println("Department constructor executed");
}
}
class Student extends Department
{
/* Constructor */
Student()
{
System.out.println("Student constructor executed");
}

}
{
/* Driver Code */
public static void main(String[] args)
{
/* Create instance of Student class */
System.out.println("Order of constructor execution in Multilevel inhe
ritance...");
new Student();
}
}
Output:
Order of constructor execution in multilevel inheritance...
College constructor executed
Department constructor executed
Student constructor executed
Program 5. Calling super class constructor using super keyword
/* Parent Class */
class ParentClass
{
int a;
ParentClass(int x)
{
a = x;
}
}

/* Child Class */
class ChildClass extends ParentClass
{
int b;
ChildClass(int x, int y)
{
/* Accessing ParentClass Constructor */
super(x);
b = y;
}
/* Method to show value of a and b */
void Show()
{
System.out.println("Value of a : "+a+"nValue of b : "+b);
}
}
{
/* Driver Code */
public static void main(String ar[])
{
System.out.println("Order of constructor execution...");
ChildClass d = new ChildClass(79, 89);
d.Show();
}
}

Multilevel Hierarchy
In simple inheritance a subclass or derived class derives the properties from its parent
class, but in multilevel inheritance a subclass is derived from a derived class. One class
inherits only single class. Therefore, in multilevel inheritance, every time ladder
increases by one. The lower most class will have the properties of all the super classes’.
Example for multilevel hierarchy:
Program-1
class A {
void funcA() {
System.out.println("This is class A");
}
}
class B extends A {
void funcB() {
System.out.println("This is class B");
}
}
class C extends B {
void funcC() {
System.out.println("This is class C");
}
}
public class Demo {
public static void main(String args[]) {
C obj = new C();
obj.funcA();
obj.funcB();
obj.funcC();
}
}
Output

This is class A
This is class B
This is class C
Program-2
class student
{
int rollno;
String name;
student(int r, String n)
{
rollno = r;
name = n;
}
void dispdatas()
{
System.out.println("Rollno = " + rollno);
System.out.println("Name = " + name);
}
}
class marks extends student
{
int total;
marks(int r, String n, int t)
{
super(r,n); //call super class (student) constructor
total = t;
}
void dispdatam()
{
dispdatas(); // call dispdatap of student class
System.out.println("Total = " + total);
}
}
class percentage extends marks
{
int per;

percentage(int r, String n, int t, int p)
{
super(r,n,t); //call super class(marks) constructor
per = p;
}
void dispdatap()
{
dispdatam(); // call dispdatap of marks class
System.out.println("Percentage = " + per);
}
}
class Multi_Inhe
{
public static void main(String args[])
{
percentage stu = new percentage(102689, "RATHEESH", 350, 70); //call constructor
percentage
stu.dispdatap(); // call dispdatap of percentage class
}
}
Output:
Rollno = 102689
Name = RATHEESH
Total = 350
Percentage = 70
Program-3
class stu
{
int rollno;
String name;
stu(int r, String n)
{
rollno = r;
name = n;
}
void show()
{
System.out.println("Student Roll no - " + rollno);
System.out.println("Student Name - " + name);
}
}
class marks extends stu

{
int s1, s2, s3, s4, s5, sum1;
marks(int r, String n, int m1, int m2, int m3, int m4, int m5)
{
super(r,n);
s1 = m1;
s2 = m2;
s3 = m3;
s4 = m4;
s5 = m5;
}
void showmarks()
{
show();
sum1 = s1 + s2 + s3 + s4 + s5;
System.out.println("Total marks = " + sum1);
}
}
class percent extends marks
{
float per;
percent(int r, String n, int m1, int m2, int m3, int m4, int m5,
float p)
{
super(r,n,m1,m2,m3,m4,m5);
per=p;
}
void showper()
{
showmarks();
per = sum1 / 5;
System.out.println("Percentage = " + per);
}
}
class multiEg
{
public static void main(String args[])
{
percent p = new percent(101, "Nancy", 90, 75, 85, 90, 80, 0);
p.showper();
}
}

Unit-3 Practice Programs-5.docx

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