Prototype Design Pattern using Java

Let’s take a look at how the Prototype can be implemented without the standard Cloneable interface. The first thing we do is create a package to place our class files. The name of this package we will call shapes. Now let's add an interface we call Shape. Shape will be an abstract class. The code for this abstract class will be

public abstract class Shape {
    public int x;
    public int y;
    public String color;
    public Shape() {
    }
    public Shape(Shape target) {
        if (target != null) {
            this.x = target.x;
            this.y = target.y;
            this.color = target.color;
        }
    }
    public abstract Shape clone();
    @Override
    public boolean equals(Object object2) {
        if (!(object2 instanceof Shape)) return false;
        Shape shape2 = (Shape) object2;
        return shape2.x == x && shape2.y == y && Objects.equals(shape2.color, color);
    }
}

Let's now create a couple of shapes. We will create a Circle class oblect. And, also we will create a Rectangle. Both the Circle and Rectangle are extended with Shape For the Circle class we have the folloing code:

public class Circle extends Shape{
    public int radius;
    public Circle() {
    }
    public Circle(Circle target) {
        super(target);
        if (target != null) {
            this.radius = target.radius;
        }
    }
    @Override
    public Shape clone() {
        return new Circle(this);
    }
    @Override
    public boolean equals(Object object2) {
        if (!(object2 instanceof Circle) || !super.equals(object2)) return false;
        Circle shape2 = (Circle) object2;
        return shape2.radius == radius;
    }
}

And for the Rectangle the code is:

public class Rectangle extends Shape {
    public int width;
    public int height;
    public Rectangle() {
    }
    public Rectangle(Rectangle target) {
        super(target);
        if (target != null) {
            this.width = target.width;
            this.height = target.height;
        }
    }
    @Override
    public Shape clone() {
        return new Rectangle(this);
    }
    @Override
    public boolean equals(Object object2) {
        if (!(object2 instanceof Rectangle) || !super.equals(object2)) return false;
        Rectangle shape2 = (Rectangle) object2;
        return shape2.width == width && shape2.height == height;
    }
}

Lastly we put this all into static void main method we place in the Demo class file. The code looks like:

public class Demo {
    public static void main(String[] args) {
        System.out.println("hello");
        List<Shape> shapes = new ArrayList<>();
        List<Shape> shapesCopy = new ArrayList<>();
        Circle circle = new Circle();
        circle.x = 10;
        circle.y = 20;
        circle.radius = 15;
        circle.color = "red";
        shapes.add(circle);
        Circle anotherCircle = (Circle) circle.clone();
        shapes.add(anotherCircle);
        Rectangle rectangle = new Rectangle();
        rectangle.width = 10;
        rectangle.height = 20;
        rectangle.color = "blue";
        shapes.add(rectangle);
        cloneAndCompare(shapes, shapesCopy);
    }

    private static void cloneAndCompare(List<Shape> shapes, List<Shape> shapesCopy) {
        for (Shape shape : shapes) {
            shapesCopy.add(shape.clone());
        }
        for (int i = 0; i < shapes.size(); i++) {
            if (shapes.get(i) != shapesCopy.get(i)) {
                System.out.println(i + ": Shapes are different objects (yay!)");
                if (shapes.get(i).equals(shapesCopy.get(i))) {
                    System.out.println(i + ": And they are identical (yay!)");
                } else {
                    System.out.println(i + ": But they are not identical (booo!)");
                }
            } else {
                System.out.println(i + ": Shape objects are the same (booo!)");
            }
        }
    }
}

Compile and run. You should get the following result:

hello
0: Shapes are different objects (yay!)
0: And they are identical (yay!)
1: Shapes are different objects (yay!)
1: And they are identical (yay!)
2: Shapes are different objects (yay!)
2: And they are identical (yay!)

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