November 2020 ~ whereisstuff

Polymorphism in java

whereisstuffNovember 30, 2020 No comments

Polymorphism:

Ploy means many and prism means form so polymorphism means many form.
It is used to perform a single action in different ways.
For example,
Action is draw and it performance may be draw a line or draw circle.

Types of polymorphism:

1. Runtime polymorphism

2. Compile time polymorphism

Runtime polymorphism:

The runtime polymorphism is also called as dynamic polymorphism.
It is best example is method overloading.

Example program:

import java.util.Scanner;
class Shape {
Scanner sc = new Scanner(System.in);
double a;
    void area() {
        System.out.println("\tCalculating area of Rectangle,Circle,Triangle .........");
    }
}

class Rectangle extends Shape {
    void area() {
        float l,w;
        System.out.println("Enter length and width of rectangle : ");
        l=sc.nextFloat();
        w=sc.nextFloat();
        a=l*w; //area=length*width;
        System.out.println("Area of rectangle : "+a);
    }
}

class Circle extends Shape {
    void area() {
        float r;
        System.out.println("Enter radius of circle : ");
        r=sc.nextFloat();
        a=3.14*r*r; //area=3.14*radius*radius;
        System.out.println("Area of circle : "+a);
    }
}

class Triangle extends Shape {
    void area() {
        double b,h;
        System.out.println("Enter base and length of triangle : ");
        b=sc.nextDouble();
        h=sc.nextDouble();
        a=(b*h)/2; //area=1/2*Base*length;
        System.out.println("Area of triangle : "+a);
    }
}

class Runtime_Polymerpism {
    public static void main(String args[]) {
        Shape s=new Shape();
        s.area();
        s = new Rectangle();
        s.area();
        s = new Circle();
        s.area();
        s = new Triangle();
        s.area();
    }

}

Output:

Compile time polymorphism:

The runtime polymorphism is also called as static polymorphism.
It is best example is method overriding.

Example program:

public class Complietime_polymorpism {
    float l, w, r;
    double a,b, h;
    void area() {
        System.out.println("\tCalculating area of Rectangle,Circle,Triangle .........");
    }

    void area(float l, float w) {
        a = l * w; //area=length*width;
        System.out.println("Area of rectangle : " + a);
    }

    void area(float r) {
        a = 3.14 * r * r; //area=3.14*radius*radius;
        System.out.println("Area of circle : " + a);
    }

    void area(double b, double h) {
        a = (b * h) / 2; //area=1/2*Base*length;
        System.out.println("Area of triangle : " + a);
    }
}

class Passing_value_through_obj {

    public static void main(String args[]) {
        Complietime_polymorpism cp = new Complietime_polymorpism();
        cp.area();
        cp.area(1, 2);
        cp.area(2);
        cp.area(8, 5);

    }

}

Output:

Note:

If you need to detail learning of method overloading and method overriding concept then please click the below link to helpful.
https://www.whereisstuff.com/2020/11/method-overloading-and-overriding-in.html

Method overloading and overriding in java

whereisstuffNovember 30, 2020 No comments

Overriding:

Method overriding is a mechanism in which a subclass inherits the methods of super class and sometimes the subclass modifies the implementation of a method defined in super class.
That means if subclass (Derived class) has the same method as declared in the parent class (base class).
Method overriding is used for runtime polymorphism.

Rules for Java Method Overriding:

The method must have the same name as in the parent class
The method must have the same parameter as in the parent class.
There must be inherited.
A static method cannot be overridden. It can be proved by runtime polymorphism.

Syntax:

class base_class_name
{
return_type method_name(parameter_list)
{
//Statement
}
}

class derived_class_name
{
base_class_method(parameter_list)
{
//Statement
}

}

Example program:

class Bank {
    int get_Rate_Of_Interest() {
        return 0;
    }
}
class SBI extends Bank {
  int get_Rate_Of_Interest() {
        return 8;
    }
}
class ICICI extends Bank {
    int get_Rate_Of_Interest() {
        return 7;
    }
}
class AXIS extends Bank {
    int get_Rate_Of_Interest() {
        return 9;
    }
}
class Method_Overriding {
    public static void main(String args[]) {
        SBI s = new SBI();
        ICICI i = new ICICI();
        AXIS a = new AXIS();
        System.out.println("SBI Rate of Interest: " + s.get_Rate_Of_Interest());
        System.out.println("ICICI Rate of Interest: " + i.get_Rate_Of_Interest());
        System.out.println("AXIS Rate of Interest: " + a.get_Rate_Of_Interest());
    }

}

Output:

Method overloading:

Overloading is a mechanism in which we can use many methods having the same function name but can pass different number of parameters or different types of parameters.

Syntax:

class base_class_name
{
return_type method_name(parameter_list)
{
//Statement
}
return_type same_method_name(parameter_list)
{
//Statement
}

}

Example program:

class SimpleCalculator
{
    int add(int a, int b)
    {
         return a+b;
    }
    int add(int a, int b, int c)
    {
         return a+b+c;
    }
}
class Method_Overloading {
   public static void main(String args[])
   {
       SimpleCalculator obj = new SimpleCalculator();
       System.out.println("Adding two number : "+obj.add(10, 20));
       System.out.println("Adding three number : "+obj.add(10, 20, 30));
   }

}

Output:

Constructor overloading in java

whereisstuffNovember 30, 2020 1 comment

Constructor overloading:

If one class has more than one constructor different parameters list called Constructor overloading.

Example program:

class StudentData
{
   private int stuID;
   private String stuName;
   private int stuAge;
   StudentData()
   {
     //Default constructor
       stuID = 1001;
       stuName = "Sabrina";
       stuAge = 15;
   }
   StudentData(int num1, String str, int num2)
   {
       //Parameterized constructor
       stuID = num1;
       stuName = str;
       stuAge = num2;
   }

   public int getStuID() {
       return stuID;
   }
   public void setStuID(int stuID) {
       this.stuID = stuID;
   }
   public String getStuName() {
       return stuName;
   }
   public void setStuName(String stuName) {
       this.stuName = stuName;
   }
   public int getStuAge() {
       return stuAge;
   }
   public void setStuAge(int stuAge) {
       this.stuAge = stuAge;
   }

   public static void main(String args[])
   {
       //This object creation would call the default constructor
       StudentData obj = new StudentData();
       System.out.println("Values from Default constructor.....");
       System.out.println("Student Name is: "+obj.getStuName());
       System.out.println("Student Age is: "+obj.getStuAge());
       System.out.println("Student ID is: "+obj.getStuID());

       System.out.println("\nValues from Parameterized constructor.....");
       StudentData obj2 = new StudentData(2005, "Kurshitha", 18);
       System.out.println("Student Name is: "+obj2.getStuName());
       System.out.println("Student Age is: "+obj2.getStuAge());
       System.out.println("Student ID is: "+obj2.getStuID());
}

}