The java code to design a new Triangle class that extends the abstract GeometricObject class and to design a test program   that prompts the user to enter three sides of the triangle, a color, and a Boolean value to indicate whether the triangle is filled or not.

Program:

File name: Exercise_13_01.java

//package to have user input

import java.util.Scanner;

//class Definition

public class Exercise_13_01

{

// Main method

public static void main(String[] args)

{

// Create a Scanner object

Scanner input = new Scanner(System.in);

/* Prompt the user to enter three sides of the triangle */

System.out.print("Enter three side of the triangle: ");

double side1 = input.nextDouble();

double side2 = input.nextDouble();

double side3 = input.nextDouble();

// Prompt the user to enter a color

System.out.print("Enter a color: ");

String color = input.next();

/*Prompt the user to enter a boolean value on whether the triangle is filled*/

System.out.print("Is the triangle filled (true / false)? ");

boolean filled = input.nextBoolean();

/* Create triangle object with the entered user input */

Triangle triangle = new Triangle(side1, side2, side3);

// set color

triangle.setColor(color);

// set filled

triangle.setFilled(filled);

// print the output

System.out.println(triangle.toString());

System.out.println("Area: " + triangle.getArea());

System.out.println("Perimeter: " + triangle.getPerimeter());

System.out.println("Color: " + triangle.getColor());

System.out.println("Triangle is" + (triangle.isFilled() ? "" : " not ")

+ "filled");

}

}

Filename: GeometricObject.java

//abstract class GeometricObject definition

public abstract class GeometricObject

{

//data type declaration

private String color = "while";

private boolean filled;

private java.util.Date dateCreated;

// Construct a default geometric object

protected GeometricObject()

{

dateCreated = new java.util.Date();

}

/* Construct a geometric object with color and filled value */

protected GeometricObject(String color, boolean filled)

{

dateCreated = new java.util.Date();

//assign color and fill

this.color = color;

this.filled = filled;

}

// Return color

public String getColor()

{

return color;

}

// Set a new color

public void setColor(String color)

{

this.color = color;

}

/* isFilled method returns filled and Since filled is boolean,the get method is named isFilled */

public boolean isFilled()

{

return filled;

}

// Set a new filled

public void setFilled(boolean filled)

{

this.filled = filled;

}

// Get dateCreated

public java.util.Date getDateCreated()

{

return dateCreated;

}

//override toString function to return output

@Override

public String toString()

{

return "created on " + dateCreated + "\ncolor: " + color +

" and filled: " + filled;

}

// define Abstract method getArea

public abstract double getArea();

//Define Abstract method getPerimeter

public abstract double getPerimeter();

}

Filename: Triangle.Java

/*Class definition of Triangle that extends the class GeometricObject */

public class Triangle extends GeometricObject

{

//declare the three sides of the triangle

private double side1;

private double side2;

private double side3;

//triangle constructor

public Triangle()

{

}

//assign values to all three sides of the triangle

public Triangle(double side1, double side2, double side3)

{

this.side1 = side1;

this.side2 = side2;

this.side3 = side3;

}

//assign triangle values to all attributes

public Triangle(double side1, double side2, double side3, String color, boolean filled)

{

this(side1, side2, side3);

setColor(color);

setFilled(filled);

}

// Return side1

public double getSide1()

{

return side1;

}

// Set side1 to a new length

public void setSide1(double side1)

{

this.side1 = side1;

}

// Return side2

public double getSide2()

{

return side2;

}

// Set side2 to a new length

public void setSide2(double side2)

{

this.side2 = side2;

}

// Return side3

public double getSide3()

{

return side3;

}

// Set side3 to a new length

public void setSide3(double side3)

{

this.side3 = side3;

}

// Function to Return area of the Triangle

@Override

public double getArea()

{

double s = (side1 + side2 + side3) / 2;

return Math.sqrt(s * (s - side1) * (s - side2) * (s - side3));

}

/* override function to Return perimeter of the triangle */

@Override

public double getPerimeter()

{

return side1 + side2 + side3;

}

/*override function to Return a string description of the object*/

@Override

public String toString()

{

return super.toString() + "\nArea: " + getArea() + "\nPerimeter: " + getPerimeter();

}

}

UML Diagram:

Explanation:

• Here, GeometricObject is an abstract class that extends the triangle class which is represented using an arrow. The triangle class then contains a rectangle that represents the objects used to input the three sides of the triangle.
• The remaining part is used to represent all the methods and functions used in the triangle class.
• The Triangle() method creates a triangle with default sides.  The method Triangle(side1:double, side2; double,side3;double) creates a triangle of the specified sides.
• Then the respective sides of the triangles are returned using getSide() methods.
• Then the method getArea() returns the area of the triangle and the method getPerimeter() returns the perimeter of the triangle and the function toString() returns a string description of the object.

Enter three side of the triangle: 3

4

5

Enter a color: red

Is the triangle filled (true / false)? false

created on Sun Jul 08 13:24:03 IST 2018

color: red and filled: false

Area: 6.0

Perimeter: 12.0

Area: 6.0

Perimeter: 12.0

Color: red

Triangle is not filled