Inheritance,JAVA
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Inheritance: Creating new class from existing class such that the features of existing class are available to the new class is called inheritance. Already existing class is called super class & produced class is called sub class. Using inheritance while creating sub classes a programmer can reuse the super class code without rewriting it.
Program 1: Write a program to create a Person class which contains general details of a person and create a sub class Employ which contains company details of a person. Reuse the general details of the person in its sub class.
// Inheritance Example class Person
{ String name;
String permanentAddress;
int age;
void set_PermanentDetails (String name, String permanentAddress, int age)
{ this.name = name;
this.permanentAddress = permanentAddress;
this.age = age;
}
void get_PermanentDetails ()
{ System.out.println ("Name : " + name);
System.out.println ("Permanent Address : " + permanentAddress);
System.out.println ("Age :" + age);
}
}
class Employ extends Person
{ int id;
String companyName;
String companyAddress;
Employ (int id, String name, String permanentAddress, int age,
String companyName, String companyAddress)
{ this.id = id;
set_PermanentDetails (name, permanentAddress, age);
this.companyName = companyName;
this.companyAddress = companyAddress;
}
void get_EmployDetails ()
{ System.out.println ("Employ Id : " + id);
get_PermanentDetails ();
System.out.println ("Company Name : "+ companyName);
System.out.println ("Company Address : "+companyAddress);
}
}
class InherDemo
{
public static void main (String args [])
Employ e1 = new Employ (101, "Suresh Kumar", "18-Madhura Nagar-Tirupati", 29, "Centris Software- Chennai", "20-RVS Nagar");
e1.get_EmployDetails ();
}
}
Output:
Program 2: Write a program to illustrate the order of calling of default constructor in super and sub class.
// Default constructors in super and sub class class One
{ One ( ) //super class default constructor
{
System.out.println ("Super class default constructor called");
}
}
class Two extends One
{ Two ( ) //sub class default constructor
{
System.out.println ("Sub class default constructor called");
}
}
class Const
{ public static void main (String args[])
{ Two t=new Two ( ); //create sub class object
}
}
Output:
· Super class default constructor is available to sub class by default.
· First super class default constructor is executed then sub class default constructor is executed.
· Super class parameterized constructor is not automatically available to subclass. super is the key word that refers to super class.
The keyword ‘super’:
· super can be used to refer super class variables as: super.variable
· super can be used to refer super class methods as: super.method ()
· super can be used to refer super class constructor as: super (values)
Program 3: Write a program to access the super class method, super class parameterized constructor and super class instance variable by using super keyword from sub class.
// super refers to super class- constructors, instance variables and methods class A
{
int x;
A (int x)
{
this.x = x;
}
void show( )
{ System.out.println("super class method: x = "+x);
}
}
class B extends A
{
int y;
B (int a,int b)
{
super(a); // (or) x=a;
y=b;
}
void show( )
{
super.show ();
System.out.println ("y = "+y);System.out.println (“ super x = “ + super.x);
}
}
class SuperUse
{
public static void main(String args[])
{ B ob = new B (10, 24);
ob.show ( );
}
}
Output:
· Super key word is used in sub class only.
· The statement calling super class constructor should be the first one in sub class constructor. Category: Inheritance Java, Java
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