版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/xiao__jia__jia/article/details/86776640
设计模式--蝇量模式
•蝇量模式原理
•景观设计软件项目遇到的问题
树：XY坐标，树的大小，外观，需要很多树
10000000棵树
思考如何设计
传统方式：
Tree
public class Tree {
private int xCoord, yCoord, age;
public Tree(int xCoord, int yCoord, int age) {
this.xCoord = xCoord;
this.yCoord = yCoord;
this.age = age;
}
public void display() {
System.out.print("x");
}
}
TreesTest
public class TreesTest {
private int length = 10000000;
private Tree[] treelst = new Tree[length];
public TreesTest() {
for (int i = 0; i < length; i++) {
treelst[i] = new Tree((int) (Math.random() * length),
(int) (Math.random() * length),
(int) (Math.random() * length) % 5);
}
}
public void display() {
for (int i = 0, len = treelst.length; i < len; i++) {
treelst[i].display();
}
}
}
MainTest
public class MainTest {
public static void main(String[] args) {
showMemInfo();
TreesTest mTreesTest;
mTreesTest = new TreesTest();
showMemInfo();
mTreesTest.display();
showMemInfo();
}
public static void showMemInfo() {
// 最大内存：
long max = Runtime.getRuntime().maxMemory();
// 分配内存：
long total = Runtime.getRuntime().totalMemory();
// 已分配内存中的剩余空间 ：
long free = Runtime.getRuntime().freeMemory();
// 已占用的内存：
long used = total - free;
System.out.println("最大内存 = " + max);
System.out.println("已分配内存 = " + total);
System.out.println("已分配内存中的剩余空间 = " + free);
System.out.println("已用内存 = " + used);
System.out.println("时间 = " + System.currentTimeMillis());
System.out.println("");
}
}思考：这些树之间有啥关系
内部状态和外部状态
TreeFlyWeight
public class TreeFlyWeight {
public TreeFlyWeight() {
}
public void display(int xCoord, int yCoord, int age) {
// System.out.print("x");
}
}
TreeManager
public class TreeManager {
private int length = 10000000;
int[] xArray = new int[length], yArray = new int[length],
AgeArray = new int[length];
private TreeFlyWeight mTreeFlyWeight;
public TreeManager() {
mTreeFlyWeight = new TreeFlyWeight();
for (int i = 0; i < length; i++) {
xArray[i] = (int) (Math.random() * length);
yArray[i] = (int) (Math.random() * length);
AgeArray[i] = (int) (Math.random() * length) % 5;
}
}
public void displayTrees() {
for (int i = 0; i < length; i++) {
mTreeFlyWeight.display(xArray[i], yArray[i], AgeArray[i]);
}
}
}
MainTest
public class MainTest {
public static void main(String[] args) {
showMemInfo();
TreeManager mTreeManager;
mTreeManager = new TreeManager();
showMemInfo();
mTreeManager.displayTrees();
showMemInfo();
}
public static void showMemInfo() {
// 已分配内存中的剩余空间 ：
long free = Runtime.getRuntime().freeMemory();
// 分配内存：
long total = Runtime.getRuntime().totalMemory();
// 最大内存：
long max = Runtime.getRuntime().maxMemory();
// 已占用的内存：
long used = total - free;
System.out.println("最大内存 = " + max);
System.out.println("已分配内存 = " + total);
System.out.println("已分配内存中的剩余空间 = " + free);
System.out.println("已用内存 = " + used);
System.out.println("时间 = " + System.currentTimeMillis());
System.out.println("");
}
}
蝇量模式原理
蝇量模式：通过共享的方式高效地支持大量细粒度的对象。
•蝇量模式优缺点
优点：
减少运行时的对象实例个数，节省创建开销和内存
将许多“虚拟”对象的状态集中管理
缺点：
系统设计更加复杂
需要专门维护对象的外部状态
•蝇量模式示例代码讲解•示例项目类结构
Plant
public abstract class Plant {
public Plant() {
}
public abstract void display(int xCoord, int yCoord, int age);
}
Grass
public class Grass extends Plant {
@Override
public void display(int xCoord, int yCoord, int age) {
// TODO Auto-generated method stub
// System.out.print("Grass x");
}
}
Tree
public class Tree extends Plant {
@Override
public void display(int xCoord, int yCoord, int age) {
// TODO Auto-generated method stub
// System.out.print("Tree x");
}
}
PlantFactory
import java.util.HashMap;
public class PlantFactory {
private HashMap<Integer, Plant> plantMap = new HashMap<Integer, Plant>();
public PlantFactory() {
}
public Plant getPlant(int type) {
if (!plantMap.containsKey(type)) {
switch (type) {
case 0:
plantMap.put(0, new Tree());
break;
case 1:
plantMap.put(1, new Grass());
break;
}
}
return plantMap.get(type);
}
}
PlantManager
public class PlantManager {
private int length = 10000000;
private int[] xArray = new int[length], yArray = new int[length],
AgeArray = new int[length], typeArray = new int[length];
private PlantFactory mPlantFactory;
public PlantManager() {
mPlantFactory=new PlantFactory();
for (int i = 0; i < length; i++) {
xArray[i] = (int) (Math.random() * length);
yArray[i] = (int) (Math.random() * length);
AgeArray[i] = (int) (Math.random() * length) % 5;
typeArray[i]= (int) (Math.random() * length) % 2;
}
}
public void displayTrees() {
for (int i = 0; i < length; i++) {
mPlantFactory.getPlant(typeArray[i]).display(xArray[i], yArray[i], AgeArray[i]);
}
}
}
MainTest
import java.util.ArrayList;
public class MainTest {
public static void main(String[] args) {
showMemInfo();
PlantManager mPlantManager;
mPlantManager = new PlantManager();
showMemInfo();
mPlantManager.displayTrees();
showMemInfo();
}
public static void showMemInfo() {
// 已分配内存中的剩余空间 ：
long free = Runtime.getRuntime().freeMemory();
// 分配内存：
long total = Runtime.getRuntime().totalMemory();
// 最大内存：
long max = Runtime.getRuntime().maxMemory();
// 已占用的内存：
long used = total - free;
System.out.println("最大内存 = " + max);
System.out.println("已分配内存 = " + total);
System.out.println("已分配内存中的剩余空间 = " + free);
System.out.println("已用内存 = " + used);
System.out.println("时间 = " + System.currentTimeMillis());
System.out.println("");
}
}
蝇量模式关键点
•蝇量模式原理
蝇量模式：通过共享的方式高效地支持大量细粒度的对象。
优点：
减少运行时的对象实例个数，节省创建开销和内存
将许多“虚拟”对象的状态集中管理
缺点：
系统设计更加复杂
需要专门维护对象的外部状态
•蝇量模式适用场合
适用场合：
•需要大量细粒度对象
•这些对象的外部状态不多
•按照内部状态分成几个组，每一个组都仅用一个蝇量对象代替