1. 定义

运用共享技术有效地支持大量细粒度的对象。

2. 实现

2.1 Tree、TreeNode、TreeFactory

class Tree {
    //设置final保证线程安全
    private final String name;
    private final String data;
    public Tree(String name, String data) {
        this.name = name;
        this.data = data;
    }
    public String getName() {
        return name;
    }
    public String getData() {
        return data;
    }
}

class TreeNode {
    private int x;
    private int y;
    private Tree tree;
    public TreeNode(int x, int y, Tree tree) {
        this.x = x;
        this.y = y;
        this.tree = tree;
    }
    public int getX() {
        return x;
    }
    public void setX(int x) {
        this.x = x;
    }
    public int getY() {
        return y;
    }
    public void setY(int y) {
        this.y = y;
    }
    public Tree getTree() {
        return tree;
    }
    public void setTree(Tree tree) {
        this.tree = tree;
    }
}

class TreeFactory {
    //ConcurrentHashMap保证线程安全
    private static Map<String, Tree> map = new ConcurrentHashMap<>();
    public static Tree getTree(String name, String data) {
        if (map.containsKey(name)) {
            return map.get(name);
        }
        Tree tree = new Tree(name, data);
        map.put(name, tree);
        return tree;
    }
}

2.2 使用

 public static void main(String[] args) {
        //TreeFactory.getTree获取的到数据只会实例化一次，就达到数据共享目的
        TreeNode treeNode1 = new TreeNode(3, 4, TreeFactory.getTree("xxx", "xxxxxxx"));
        TreeNode treeNode2 = new TreeNode(5, 9, TreeFactory.getTree("xxx", "xxxxxxx"));
    }

3. 优点

如果系统有大量类似的对象，可以节省大量的内存及CPU资源

4. JDK源码应用

String,Integer,Long...
com.sun.org.apache.bcel.internal.generic.InstructionConstants