Question

Based on the particle example redo the areashapes assignment to implement the polymorphism concept (via method overloading and overriding) whereby the user selects a shape, and the program calculates, and displays the shape's area using "displayArea()" .

/*
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* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package areashapes;

/**
*
* @author Maore
*/

public class AreaShapes{
public static void main(String[] args) {
Circle c=new Circle();
Triangle t= new Triangle();
Trapezium tz= new Trapezium();
Oval o= new Oval();


System.out.println("Area of the Circle:"+c.area());//single inheritance
System.out.println("Area of the Triangle is:" + t.area());
System.out.println("Area of the Trapezium is:" + tz.area());
System.out.println("Area of the Oval is:" + o.area());
MethodsRectangle mr=new MethodsRectangle();//method overloading
  

//the data type is integer therefore displayArea method will be invoked.
System.out.println("Area of the Rectangle:"+mr.displayArea(3, 4));
//double data type therefore double type method will be invoked
System.out.println("Area of the Rectangle:"+mr.displayArea(3.4, 4.3));
  
  
//method overriding
Dimensions d=new MethodsRectangle();
d.displayArea();//this will get the method displayArea from the MethodsRectangle class not from the Dimensions class because it is overridden by the
//child class
  
  
//final keyword
final double unchangeble=1;
  
System.out.print(unchangeble);
  
}
}
class Dimensions{ //parent or base class
double radius=7;
double pi= 8;//circle
double length,width;//rectangle
double base,height;//triangle
double a=14,b=16,h=19;//trapezium;
double a1,b1;//oval;
  
//method override
public void displayArea() {
System.out.print("Display Area");
}
  
}

//single inheritance
class Circle extends Dimensions{
  
public double area() {
return (super.pi*super.radius*super.radius);
// super keyword to get the variables of the previous class
}
}

//hierarchical inheritance i.e.,all every class in the program inheriting the parent class
// Circle class included in this hierarchical inheritance)

class Triangle extends Dimensions{
double base=7;
double height= 8;
  
  
public double area() {
return(this.base*this.height);//here we've used this keyword for access the variable of current class


}
}

class Trapezium extends Dimensions{
  
public double area() {
return((super.a+super.height)/2)*super.h;//super keyword to access the variable of current class
}
}
  
  
  
class Oval extends Dimensions{
double a1= 16;
double b1=20;
double pi= 3.14;
public double area() {
return((this.a1*this.b1*this.pi)/2);//this keyword to access the variable of current class
}
}
//and finally we will look into the method overloading and method overriding in this class

class MethodsRectangle extends Dimensions{
public int displayArea(int x,int y) {// this method gives area for integer dimensions
return(x*y);
}
public double displayArea(double x,double y) {
return(x*y);//this method will give area for double type dimensions
}
public void displayArea() {
System.out.print("\nparent class method overriden by this class method !!! ");//this method will override the method in Dimensions class
}
  
}

  

  

Answer 1

Note: All comments starting with ### are theones made by me. Let me know in the comments if you think something else needs to be done.

import java.util.Scanner;
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
// package areashapes; //### didnt know its intent, so have commented. you can uncomment it if you want

/**
*
* @author Maore
*/

public class Main{
    public static void main(String[] args) {
        Scanner myObj = new Scanner(System.in);
        
        // ### I am using the switch menu to enable user selection
        System.out.print("Enter the option number to select the shape (1-circle 2-triangle 3-trapezium 4-oval 5-rectangle): ");
        int i=myObj.nextInt();
        switch(i){
            case 1:
                Circle c=new Circle();
                System.out.println("Area of the Circle:"+c.displayArea());//single inheritance
                break;
            case 2:
                Triangle t= new Triangle();
                System.out.println("Area of the Triangle is:" + t.displayArea());
                break;
            case 3:
                Trapezium tz= new Trapezium();
                System.out.println("Area of the Trapezium is:" + tz.displayArea());
                break;
            case 4: 
                Oval o= new Oval();
                System.out.println("Area of the Oval is:" + o.displayArea());
                break;
            case 5:
                MethodsRectangle mr=new MethodsRectangle();//method overloading
                Dimensions d=new MethodsRectangle();
                //the data type is integer therefore displayArea method will be invoked.
                System.out.println("Area of the Rectangle:"+mr.displayArea(3, 4));
                //double data type therefore double type method will be invoked
                System.out.println("Area of the Rectangle:"+mr.displayArea(3.4, 4.3));
                d.displayArea();//this will get the method displayArea from the MethodsRectangle class not from the Dimensions class because it is overridden by the
                //child class
                break;
            default: //### entering anything else wil result in this output
                //method overriding
                Dimensions dim=new Dimensions();
                dim.displayArea();
        }
        
          
        // ### dont think the following are of any use so have commented
        //final keyword
        // final double unchangeble=1;
        // System.out.print(unchangeble);
          
    }
}

class Dimensions{ //parent or base class
    double radius=7;
    double pi= 8;//circle
    double length,width;//rectangle
    double base,height;//triangle
    double a=14,b=16,h=19;//trapezium;
    double a1,b1;//oval;
      
    //method override
    public double displayArea() {
        System.out.print("No shape seleted to show the display area.");//### Text modified to suite the program
        return 0;
    }
}

//single inheritance
class Circle extends Dimensions{
  
    public double displayArea() {
        return (super.pi*super.radius*super.radius);
        // super keyword to get the variables of the previous class
    }
}

//hierarchical inheritance i.e.,all every class in the program inheriting the parent class
// Circle class included in this hierarchical inheritance)
class Triangle extends Dimensions{
    double base=7;
    double height= 8;
      
    public double displayArea() { //### Changed the name of the funciton to displayArea
        return(this.base*this.height);//here we've used this keyword for access the variable of current class
    }
}

class Trapezium extends Dimensions{
    public double displayArea() { //### Changed the name of the funciton to displayArea
        return((super.a+super.height)/2)*super.h;//super keyword to access the variable of current class
    }
}
  
class Oval extends Dimensions{
    double a1= 16;
    double b1=20;
    double pi= 3.14;
    public double displayArea() { //### Changed the name of the funciton to displayArea
        return((this.a1*this.b1*this.pi)/2);//this keyword to access the variable of current class
    }
}

//and finally we will look into the method overloading and method overriding in this class
class MethodsRectangle extends Dimensions{
    public int displayArea(int x,int y) {// this method gives area for integer dimensions
        return(x*y);
    }
    public double displayArea(double x,double y) {
        return(x*y);//this method will give area for double type dimensions
    }
    // ### Not sure if changes need to be made here too, since no value of x and y is given in the class
    public double displayArea() {
        System.out.print("\nparent class method overriden by this class method !!! ");//this method will override the method in Dimensions class
        return 0;
    }
}