Getting run time input in Abstract class in Java

Question

Problem Statement is "To develop a Java Program to create an abstract class named Shape that contains two integers and an empty method named printArea(). Provide three classes named Rectangle, Triangle and Circle such that each one of the classes extends the class Shape. Each one of the classes contains only the method printArea() that prints the area of the given shape."

In this program, I want to get the two integer values contained by the abstract class Shape, from the user (run time) instead of compile time.

This is my code

abstract class Shape

{   

    abstract void Printarea();

    int a=10,b=2;;

}

class Rectangle extends Shape

{

    void Printarea()

    {       

       System.out.println("area of rectangle is "+(a*b));

    }

}     

class Triangle extends Shape

{

    void Printarea()

    {       

        System.out.println("area of triangle is "+(0.5*a*b));

    }

}   



class Circle extends Shape

{       

    void Printarea()

   {       

        System.out.println("area of circle is "+(3.14*a*a));

   }  

}   

class Main

{

    public static void main(String []args)       

    {     

       Shape=b;

       b=new Circle();      

       b.Printarea();

       b=new Rectangle();

       b.Printarea();    

       b=new Triangle();

       b.Printarea();

   }

}

Possible duplicate of [How can I read input from the console using the Scanner class in Java?](https://stackoverflow.com/questions/11871520/how-can-i-read-input-from-the-console-using-the-scanner-class-in-java) — Coder-Man, Jul 29 '18 at 12:07
he dont want scanner. he want to initialize value a, b. i thought it — GolamMazid Sajib, Jul 29 '18 at 12:08
@sajib OP wants to get integer values from user at run time. Values are already initialized at abstract class. — Emre Dalkiran, Jul 29 '18 at 12:10
@sajib I want to get the values from user at run time in the abstract class itself not in main method! — Kishan, Jul 29 '18 at 12:13
The problem statement mentioned that the abstract class should contain two integer values! — Kishan, Jul 29 '18 at 12:15
I want to read those values from the console! I know Scanner would help me to get those values from user.If I get the values of the integers via Scanner in the abstract class, how can I able to invoke them since we can't create object for abstract class! @sajib — Kishan, Jul 29 '18 at 12:24
Part of being a good citizen here is upvoting good answers and selecting an answer that solved your problem. If one of these answers was helpful to you, please upvote and select it as the answer. — Thom, Apr 21 '20 at 15:14

score 0 · Answer 1 · answered Jul 29 '18 at 12:19

Add Setter and getter method for variables a,b ; here's my code

package com.docker.container.controllers;

 /**
 * @author atwa Jul 29, 2018
 */
public abstract class Shape {

abstract void Printarea();

int a = 10, b = 2;

/**
 * @return the a
 */
public int getA() {
    return a;
}

/**
 * @param a
 *            the a to set
 */
public void setA(int a) {
    this.a = a;
}

/**
 * @return the b
 */
public int getB() {
    return b;
}

/**
 * @param b
 *            the b to set
 */
public void setB(int b) {
    this.b = b;
}

static public class Rectangle extends Shape {

    void Printarea()

    {

        System.out.println("area of rectangle is " + (a * b));

    }

}

static class Triangle extends Shape

{

    void Printarea()

    {

        System.out.println("area of triangle is " + (0.5 * a * b));

    }

}

static class Circle extends Shape

{

    void Printarea()

    {

        System.out.println("area of circle is " + (3.14 * a * a));

    }

}

// area of circle is 314.0
// area of rectangle is 20
// area of triangle is 10.0
public static void main(String[] args)

{

    Shape b = new Circle();
    b.setA(5);
    b.setB(5);

    b.Printarea();

    b = new Rectangle();

    b.Printarea();

    b = new Triangle();

    b.Printarea();

}

}

GolamMazid Sajib · Answer 2 · 2018-07-29T12:33:25.030

Try with this:

public class Main {

public static void main(String[] args) {
    Shape b;

    Scanner in = new Scanner(System.in);
    int x = in.nextInt();
    int y = in.nextInt();

    b = new Circle(x, y);

    b.Printarea();

    b = new Rectangle(x, y);

    b.Printarea();

    b = new Triangle(x, y);

    b.Printarea();

}

private static int Abs(int a) {
    return a < 0 ? -a : a;
}
}

abstract class Shape {

int a, b;

public Shape(int a, int b) {
    this.a = a;
    this.b = b;
}

abstract void Printarea();

}

class Rectangle extends Shape {
 public Rectangle(int a, int b) {
    super(a, b);
}

void Printarea()

{

    System.out.println("area of rectangle is " + (a * b));

}

}

class Triangle extends Shape {
public Triangle(int a, int b) {
    super(a, b);
}

void Printarea()

{

    System.out.println("area of triangle is " + (0.5 * a * b));

}

}

score 0 · Answer 3 · answered Jul 29 '18 at 12:24

0

you can use Scanner class like this

public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    int i = scan.nextInt();
}

answered Jul 29 '18 at 12:24

Ehsan Shams Seir

3
3

score 0 · Answer 4 · answered Jul 29 '18 at 12:28

Some quick code but works as expected and would give you idea:

import java.util.Scanner;

abstract class Shape {

    int a = 10, b = 2;

    Shape(int a, int b){
        this.a=a;
        this.b=b;
    }

    abstract void Printarea();

}

class Rectangle extends Shape {

    Rectangle(int a, int b) {
        super(a, b);
    }

    void Printarea() {
        System.out.println("area of rectangle is " + (a * b));
    }

}

class Triangle extends Shape {

    Triangle(int a, int b) {
        super(a, b);
    }

    void Printarea(){
        System.out.println("area of triangle is " + (0.5 * a * b));
    }

}

class Circle extends Shape {

    Circle(int a, int b) {
        super(a, b);
    }

    void Printarea() {
        System.out.println("area of circle is " + (3.14 * a * a));
    }

}

class Z {

    public static void main(String[] args){

        Shape shape=null;

        String input;
        int width, height;

        while (true) {

            Scanner scanner = new Scanner(System.in);

            System.out.println("which shape? circle/rectangle/triangle (write any other thing for quitting): ");
            input = scanner.nextLine();

            if(!"circle".equalsIgnoreCase(input) && !"rectangle".equalsIgnoreCase(input) && !"triangle".equalsIgnoreCase(input) ){
                System.exit(0);
            }

            System.out.println("height: ");
            height  = scanner.nextInt();

            System.out.println("width: ");
            width = scanner.nextInt();

            if("circle".equalsIgnoreCase(input)){
                shape=new Circle(width, height);
            }
            else if("rectangle".equalsIgnoreCase(input)){
                shape=new Rectangle(width, height);
            }
            else{ // == triangle
                shape=new Triangle(width, height);
            }

            shape.Printarea();

        }

    }

}

Getting run time input in Abstract class in Java

4 Answers4