Java Example

• forest

  • forest/Forest.java

    package refactoring_guru.flyweight.example.forest;
    
    import refactoring_guru.flyweight.example.trees.Tree;
    import refactoring_guru.flyweight.example.trees.TreeFactory;
    import refactoring_guru.flyweight.example.trees.TreeType;
    
    import javax.swing.*;
    import java.awt.*;
    import java.util.ArrayList;
    import java.util.List;
    
    public class Forest extends JFrame {
        private List<Tree> trees = new ArrayList<>();
    
        public void plantTree(int x, int y, String name, Color color, String otherTreeData) {
            TreeType type = TreeFactory.getTreeType(name, color, otherTreeData);
            Tree tree = new Tree(x, y, type);
            trees.add(tree);
        }
    
        @Override
        public void paint(Graphics graphics) {
            for (Tree tree : trees) {
                tree.draw(graphics);
            }
        }
    }

• trees

  • trees/Tree.java

    package refactoring_guru.flyweight.example.trees;
    
    import java.awt.*;
    
    public class Tree {
        private int x;
        private int y;
        private TreeType type;
    
        public Tree(int x, int y, TreeType type) {
            this.x = x;
            this.y = y;
            this.type = type;
        }
    
        public void draw(Graphics g) {
            type.draw(g, x, y);
        }
    }

  • trees/TreeFactory.java

    package refactoring_guru.flyweight.example.trees;
    
    import java.awt.*;
    import java.util.HashMap;
    import java.util.Map;
    
    public class TreeFactory {
        static Map<String, TreeType> treeTypes = new HashMap<>();
    
        public static TreeType getTreeType(String name, Color color, String otherTreeData) {
            TreeType result = treeTypes.get(name);
            if (result == null) {
                result = new TreeType(name, color, otherTreeData);
                treeTypes.put(name, result);
            }
            return result;
        }
    }

  • trees/TreeType.java

    package refactoring_guru.flyweight.example.trees;
    
    import java.awt.*;
    
    public class TreeType {
        private String name;
        private Color color;
        private String otherTreeData;
    
        public TreeType(String name, Color color, String otherTreeData) {
            this.name = name;
            this.color = color;
            this.otherTreeData = otherTreeData;
        }
    
        public void draw(Graphics g, int x, int y) {
            g.setColor(Color.BLACK);
            g.fillRect(x - 1, y, 3, 5);
            g.setColor(color);
            g.fillOval(x - 5, y - 10, 10, 10);
        }
    }

• Demo.java

package refactoring_guru.flyweight.example;

import refactoring_guru.flyweight.example.forest.Forest;

import java.awt.*;

public class Demo {
    static int CANVAS_SIZE = 500;
    static int TREES_TO_DRAW = 1000000;
    static int TREE_TYPES = 2;

    public static void main(String[] args) {
        Forest forest = new Forest();
        for (int i = 0; i < Math.floor(TREES_TO_DRAW / TREE_TYPES); i++) {
            forest.plantTree(random(0, CANVAS_SIZE), random(0, CANVAS_SIZE),
                    "Summer Oak", Color.GREEN, "Oak texture stub");
            forest.plantTree(random(0, CANVAS_SIZE), random(0, CANVAS_SIZE),
                    "Autumn Oak", Color.ORANGE, "Autumn Oak texture stub");
        }
        forest.setSize(CANVAS_SIZE, CANVAS_SIZE);
        forest.setVisible(true);

        System.out.println(TREES_TO_DRAW + " trees drawn");
        System.out.println("---------------------");
        System.out.println("Memory usage:");
        System.out.println("Tree size (8 bytes) * " + TREES_TO_DRAW);
        System.out.println("+ TreeTypes size (~30 bytes) * " + TREE_TYPES + "");
        System.out.println("---------------------");
        System.out.println("Total: " + ((TREES_TO_DRAW * 8 + TREE_TYPES * 30) / 1024 / 1024) +
                "MB (instead of " + ((TREES_TO_DRAW * 38) / 1024 / 1024) + "MB)");
    }

    private static int random(int min, int max) {
        return min + (int) (Math.random() * ((max - min) + 1));
    }
}

1000000 trees drawn
---------------------
Memory usage:
Tree size (8 bytes) * 1000000
+ TreeTypes size (~30 bytes) * 2
---------------------
Total: 7MB (instead of 36MB)