·如果一个应用程序使用大量的对象,造成很大的存储开销
·蝇量(享元)模式：
·蝇量模式运用共享技术有效地支持大量细粒度的对象
·蝇量模式的重点在于区分对象的共享变量(内部状态)和不可共享变量(外部状态，将此类变量从类从剔除，由外部传入)
·蝇量的优点：
·减少运行时对象实例的个数，节省内存
·将许多“虚拟”对象的状态集中管理
·蝇量的用途：
·当一个类有许多的实例，而这些实例能被同一方法控制的时候，我们就可以使用蝇量模式
·蝇量的缺点：
·享元模式使得系统更加复杂。为了使对象可以共享，需要将一些状态外部化，这使得程序的逻辑复杂化。另外它将享元对象的状态外部化，而读取外部状态使得运行时间稍微变长
·简单描述：
·享元类, 将享元类的状态分为共享变量(内部状态)和不可共享变量(外部状态，将此类变量从类从剔除，由外部传入)
·创建并管理共享对象的类,当用户请求一个共享对象时,该类的对象提供一个已创建的实例或者创建一个(如果不存在的话)
·客户类,持有享元类对象引用,并计算或存储其外部状态
public abstract class Tree {
protected double x;
protected double y;
protected int age;
protected String name;
public Tree(){
}
public Tree(int age){
this.age = age;
}
public Tree(double x, double y, int age){
this.x = x;
this.y = y;
this.age = age;
}
public void display(){
String prompt = null;
if(age>10){
prompt = "old";
}else{
prompt = "young";
}
System.out.println("["+prompt+":x-"+x+", y-"+y+"]");
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public double getX() {
return x;
}
public void setX(double x) {
this.x = x;
}
public double getY() {
return y;
}
public void setY(double y) {
this.y = y;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
----------------------
public class PhoenixTree extends Tree {
public PhoenixTree(){
super();
this.name = "PhoenixTree";
}
@Override
public void display() {
System.out.print(name+"#");
super.display();
}
}
----------------------
public class Peach extends Tree {
public Peach(){
super();
this.name = "Peach";
}
@Override
public void display() {
System.out.print(name+"#");
super.display();
}
}
----------------------
public class Osier extends Tree {
public Osier(){
super();
this.name = "Osier";
}
@Override
public void display() {
System.out.print(name+"#");
super.display();
}
}
----------------------
public class DummyTree extends Tree {
public DummyTree(){
super();
this.name = "DummyTree";
}
@Override
public void display() {
System.out.print(name+"#");
super.display();
}
}
----------------------
public class TreeManager {
private static volatile TreeManager instance;
private static HashMap<String,Tree> pool= new HashMap<String,Tree>();
private TreeManager(){
pool.put("Osier", new Osier());
pool.put("PhoenixTree", new PhoenixTree());
}
public static TreeManager getInstance(){
if(instance==null){
synchronized (TreeManager.class) {
if(instance==null){
instance = new TreeManager();
}
}
}
return instance;
}
@SuppressWarnings("finally")
public Tree getTree(String name){
Tree tree = null;
tree = pool.get(name);
if(tree != null){
return tree;
}else{
try {
Class<?> clazz = Class.forName("com.pattern.flyweight."+name);
pool.put(name, (Tree)clazz.newInstance());
} catch (Exception e) {
if(!pool.containsKey("DummyTree")){
pool.put("DummyTree", new DummyTree());
}
name = "DummyTree";
}finally{
return pool.get(name);
}
}
}
}
----------------------
public class Park {
Tree tree;
public void draw(){
double[][] treesPosInfo = {
{12.3,19.2}, {2.3,1.2}, {32.3,9.2},
{112.3,129.2}, {11.3,1329.2}, {1211.3,1.2},
{12.3,19.2}, {2.3,1.2}, {32.3,9.2},
{112.3,129.2}, {11.3,1329.2}, {1211.3,1.2},
{12.3,19.2}, {2.3,1.2}, {32.3,9.2},
{112.3,129.2}, {11.3,1329.2}, {1211.3,1.2},
{12.3,19.2}, {2.3,1.2}, {32.3,9.2},
{112.3,129.2}, {11.3,1329.2}, {1211.3,1.2},
{12.3,19.2}, {2.3,1.2}, {32.3,9.2},
{112.3,129.2}, {11.3,1329.2}, {1211.3,1.2},
{12.3,19.2}, {2.3,1.2}, {32.3,9.2},
{112.3,129.2}, {11.3,1329.2}, {1211.3,1.2},
{12.3,19.2}, {2.3,1.2}, {32.3,9.2},
{112.3,129.2}, {11.3,1329.2}, {1211.3,1.2},
{12.3,19.2}, {2.3,1.2}, {32.3,9.2},
{112.3,129.2}, {11.3,1329.2}, {1211.3,1.2},
{12.3,19.2}, {2.3,1.2}, {32.3,9.2},
{112.3,129.2}, {11.3,1329.2}, {1211.3,1.2},
{12.3,19.2}, {2.3,1.2}, {32.3,9.2},
{112.3,129.2}, {11.3,1329.2}, {1211.3,1.2}
};
int[] treesAgeInfo = {7, 8, 9, 10, 11, 12, 7, 8, 9, 10, 11, 12
, 7, 8, 9, 10, 11, 12, 7, 8, 9, 10, 11, 12
, 7, 8, 9, 10, 11, 12, 7, 8, 9, 10, 11, 12
, 7, 8, 9, 10, 11, 12, 7, 8, 9, 10, 11, 12
, 7, 8, 9, 10, 11, 12, 7, 8, 9, 10, 11, 12
};
TreeManager manager = TreeManager.getInstance();
for(int i=0; i<treesPosInfo.length; i++){
System.out.print("tree@"+i+"\t");
int temp = i%4;
if(temp==0){
tree = manager.getTree("Osier");
tree.setX(treesPosInfo[i][0]);
tree.setY(treesPosInfo[i][1]);
tree.setAge(treesAgeInfo[i]);
tree.display();
}else if(temp==1){
tree = manager.getTree("PhoenixTree");
tree.setX(treesPosInfo[i][0]);
tree.setY(treesPosInfo[i][1]);
tree.setAge(treesAgeInfo[i]);
tree.display();
}else if(temp==2){
tree = manager.getTree("Peach");
tree.setX(treesPosInfo[i][0]);
tree.setY(treesPosInfo[i][1]);
tree.setAge(treesAgeInfo[i]);
tree.display();
}else{
tree = manager.getTree("apple");
tree.setX(treesPosInfo[i][0]);
tree.setY(treesPosInfo[i][1]);
tree.setAge(treesAgeInfo[i]);
tree.display();
}
}
}
}
----------------------