کلاس های ابستراکت (انتزاعی) در جاوا

public abstract class MyAbstractClass{
...
}
                        

public abstract class GeometricShape {

    private final Date dateCreated = new Date();
    private String color;
    private boolean filled;

    public GeometricShape(String color, boolean filled){
        this.color = color;
        this.filled = filled;
    }

    public String getColor() {
        return color;
    }

    public void setColor(String color) {
        this.color = color;
    }

    public Date getDateCreated() {
        return dateCreated;
    }


    public boolean isFilled() {
        return filled;
    }

    public void setFilled(boolean filled) {
        this.filled = filled;
    }

    //تعریف متد های مساحت و محیط به صورت ابستراکت
    public abstract double getArea();
    public abstract double getPerimeter();


    @Override
    public String toString() {
        if(this instanceof Circle)
            return "Circle: created on " + getDateCreated().toString() + "\n" + " area: " + getArea() +
            " perimeter " + getPerimeter();
        else
            return "Rectangle: created on " + getDateCreated().toString() + "\n" + " area: " + getArea()
            + " perimeter: " + getPerimeter();
    }

  }

class Circle extends GeometricShape{
    private double radius;

    public Circle(double radius, String color, boolean filled){
        super(color, filled);
        this.radius = radius;
    }

    public Circle(double radius){
        this(radius, "white", false);
    }

    public double getRadius() {
        return radius;
    }

    public void setRadius(double radius) {
        this.radius = radius;
    }

    //پیاده سازی کامل متد های مساحت و محیط

    @Override
    public double getArea(){
        return Math.PI * radius * radius;
    }

    @Override
    public double getPerimeter(){
        return 2 * Math.PI * radius;
    }

    @Override
    public boolean equals(Object obj) {
        if (obj instanceof Circle)
            return ((Circle) obj).radius == this.radius;

        return false;
    }

}

class Rectangle extends GeometricShape{
    private double width;
    private double height;

    public Rectangle(double width , double height, String color, boolean filled){
        super(color, filled);
        this.width = width;
        this.height = height;
    }

    public Rectangle(){
        this(1.0, 1.0, "White", true);
    }

    public double getWidth() {
        return width;
    }

    public void setWidth(double width) {
        this.width = width;
    }

    public double getHeight() {
        return height;
    }

    public void setHeight(double height) {
        this.height = height;
    }

    //پیاده سازی کامل متد های مساحت و محیط
    @Override
    public double getArea(){
        return width * height;
    }

    @Override
    public double getPerimeter(){
        return (width + height) * 2;
    }


    @Override
    public String toString() {
        return "Rectangle: created on " + getDateCreated().toString() + "\n" +
        "width: " + getWidth() + " height: " + getHeight() + " area: " + getArea() + " perimeter: "
        + getPerimeter();
    }

    @Override
    public boolean equals(Object obj) {
        if (obj instanceof Rectangle){
            Rectangle r = (Rectangle) obj;
            return r.width == this.width && r.height == this.height;
        }

        return false;
    }
}
                        

public static void main(String[] args){

    GeometricShape circle = new Circle();
    System.out.println(circle.toString());

    GeometricShape rectangle = new Rectangle();
    System.out.println(rectangle.toString());

}