Flyweight

1// Flyweight (Intrinsic State)
2public class TreeType {
3    private String name;
4    private String color;
5    private String texture;
6    
7    public TreeType(String name, String color, String texture) {
8        this.name = name;
9        this.color = color;
10        this.texture = texture;
11    }
12    
13    public void draw(int x, int y) {
14        System.out.println("Drawing " + name + " tree of color " + color + " at (" + x + "," + y + ")");
15    }
16}
17
18// Flyweight Factory
19import java.util.HashMap;
20import java.util.Map;
21
22public class TreeFactory {
23    private static Map<String, TreeType> treeTypes = new HashMap<>();
24    
25    public static TreeType getTreeType(String name, String color, String texture) {
26        String key = name + "-" + color + "-" + texture;
27        if (!treeTypes.containsKey(key)) {
28            treeTypes.put(key, new TreeType(name, color, texture));
29            System.out.println("Created new TreeType: " + name);
30        }
31        return treeTypes.get(key);
32    }
33}
34
35// Context Object (Extrinsic State)
36public class Tree {
37    private int x;
38    private int y;
39    private TreeType type;
40    
41    public Tree(int x, int y, TreeType type) {
42        this.x = x;
43        this.y = y;
44        this.type = type;
45    }
46    
47    public void draw() {
48        type.draw(x, y);
49    }
50}
51
52// Client
53import java.util.ArrayList;
54import java.util.List;
55
56public class Forest {
57    private List<Tree> trees = new ArrayList<>();
58    
59    public void plantTree(int x, int y, String name, String color, String texture) {
60        TreeType type = TreeFactory.getTreeType(name, color, texture);
61        Tree tree = new Tree(x, y, type);
62        trees.add(tree);
63    }
64    
65    public void draw() {
66        for (Tree tree : trees) {
67            tree.draw();
68        }
69    }
70    
71    public static void main(String[] args) {
72        Forest forest = new Forest();
73        // Plants 100 trees, but only creates 2 TreeType objects (intrinsic state)
74        for (int i = 0; i < 50; i++) {
75            forest.plantTree(i, i, "Oak", "Green", "Rough");
76            forest.plantTree(i*2, i*2, "Pine", "Dark Green", "Smooth");
77        }
78        forest.draw();
79    }
80}