Design Pattern: Flyweight

package com.designpattern;

//Flyweight ball class representing shared intrinsic attributes
//These attributes will not change for given "ballColor" and "ballImageURL" (so, no setter methods)
public class FlyweightBall {

 private String ballColor;
 private String ballImageURL;
 
 public FlyweightBall(String ballColor, String ballImageURL) {
  this.ballColor = ballColor;
  this.ballImageURL = ballImageURL;
 }

 public String getBallColor() {
  return ballColor;
 }

 public String getBallImageURL() {
  return ballImageURL;
 }

 public void setBallColor(String ballColor) {
  this.ballColor = ballColor;
 }

 public void setBallImageURL(String ballImageURL) {
  this.ballImageURL = ballImageURL;
 }
 
}

package com.designpattern;

//Ball class representing individual balls with unique extrinsic attributes
//This will have getters and setters for values which are dynamic
public class Ball {

 //reference to the intrinsic values
 private FlyweightBall flyweightBall;
 
    private int coordinateX;
    private int coordinateY;
    private int radius;
    
    //constructor to set the intrinsic value
    //every ball must have some value for X and Y coordinates, so we can set them using constructor itself here
    public Ball(FlyweightBall flyweightBall, int coordinateX, int coordinateY) {
        this.flyweightBall = flyweightBall;
        this.coordinateX = coordinateX;
        this.coordinateY = coordinateY;
    }

 public FlyweightBall getFlyweightBall() {
  return flyweightBall;
 }

 public void setFlyweightBall(FlyweightBall flyweightBall) {
  this.flyweightBall = flyweightBall;
 }

 public int getCoordinateX() {
  return coordinateX;
 }

 public void setCoordinateX(int coordinateX) {
  this.coordinateX = coordinateX;
 }

 public int getCoordinateY() {
  return coordinateY;
 }

 public void setCoordinateY(int coordinateY) {
  this.coordinateY = coordinateY;
 }

 public int getRadius() {
  return radius;
 }

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

 @Override
 public String toString() {
  return "Ball [flyweightBall=" + flyweightBall + ", coordinateX=" + coordinateX + ", coordinateY=" + coordinateY
    + ", radius=" + radius + "]";
 }
 
}

package com.designpattern;

import java.util.HashMap;
import java.util.Map;

//BallFactory class for creating and managing FlyweightBall objects
//This is like a cache. The "FlyweightBall" for a given "ballColor" and "ballImageURL" will not change
//So, it checks it an object with a given "ballColor" and "ballImageURL" already exists. If so, return it. 
//This is where we are saving memory because for thousands of balls, we are referring to the same Flyweight object
public class BallFactory {

 private static Map<String, FlyweightBall> ballPool = new HashMap<>();

 public static FlyweightBall getFlyweightBall(String color, String imageURL) {
  
  String key = color + "_" + imageURL;

  // Check if a flyweight ball with the same intrinsic attributes already exists
  if (ballPool.containsKey(key)) {
   return ballPool.get(key);
  } else {
   // If not, create a new flyweight ball and add it to the pool
   FlyweightBall flyweightBall = new FlyweightBall(color, imageURL);
   ballPool.put(key, flyweightBall);
   return flyweightBall;
  }
 }

}

package com.demo;

import com.designpattern.Ball;
import com.designpattern.BallFactory;

public class App {

 public static void main(String[] args) {
   
  //this will create a new flyweight ball object for key = color + "_" + imageURL;
  Ball redBall1 = new Ball(BallFactory.getFlyweightBall("red", "redball.png"), 100, 200);
  //since key = color + "_" + imageURL will be the same, it will re-use the existing flyweight object
  Ball redBall2 = new Ball(BallFactory.getFlyweightBall("red", "redball.png"), 200, 300);

  //we can set other extrinsic properties like the radius by calling the setter method.
  
  System.out.println("BALL 1:");
  System.out.println(redBall1);
  System.out.println(redBall1.getFlyweightBall().getBallColor());
  System.out.println(redBall1.getFlyweightBall().getBallImageURL());
  
  
  System.out.println();
  
  System.out.println("BALL 2:");
  System.out.println(redBall2);
  System.out.println(redBall2.getFlyweightBall());
  System.out.println(redBall2.getFlyweightBall().getBallColor());
  System.out.println(redBall2.getFlyweightBall().getBallImageURL());
  
 }
 
}