Example of Composite Design pattern

Main.java

package com.company;


import java.util.ArrayList;

interface Shape{
    void draw(String fillColor);
}

class Square implements Shape{

    @Override
    public void draw(String fillColor) {
        System.out.print("Filling in the square with " + fillColor);
    }
}

class Circle implements Shape{

    @Override
    public void draw(String fillColor) {
        System.out.println("Filling in the circle with " + fillColor);
    }
}

class WhiteBoard implements Shape {

    private ArrayList<Shape> shapes;
    public WhiteBoard(ArrayList<Shape> shapes) {
        this.shapes = shapes;
    }

    @Override
    public void draw(String fillColor) {
        shapes.forEach((shape) -> {
            shape.draw(fillColor);
        });
    }
}


public class Main {

    public static void main(String[] args) {
	// write your code here
        ArrayList<Shape> shapes = new ArrayList<>();
        shapes.add(new Circle());
        shapes.add(new Square());
        WhiteBoard whiteBoard = new WhiteBoard(shapes);
        whiteBoard.draw("Red");
    }
}