设计模式（10）--蝇量模式

Posted 2023-01-06

• 蝇量模式（轻量级模式）也叫享元模式（共用一个方法）
• 景观设计软件项目遇到的问题：

• 设置一个公园或者小区，会有树的大小，外观等等
• 虽然对象不复杂，但是如果量大就会消耗很多内存，比如10000000棵树

• 代码分析：

package yingliangmoshi.old;


/**
* Created with IntelliJ IDEA.
* Description:
* User: wjx
* Date: 2019-05-06
* Time: 19:07
*/
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.println(xCoord);
    

package yingliangmoshi.old;


/**
* Created with IntelliJ IDEA.
* Description:
* User: wjx
* Date: 2019-05-06
* Time: 19:09
*/
public class TreesTest 
    private int length = 1000000;
    private Tree[] treeList = new Tree[length];
    public TreesTest()
        for(int i = 0;i<length;i++)
            treeList[i] = new Tree((int)(Math.random() * length), (int)(Math.random() * length), (int)(Math.random() * length)%5);
        
    


    public void display() 
        for(int i =  0; i<treeList.length;i++)
            treeList[i].display();
        
    

package yingliangmoshi.old;


/**
* Created with IntelliJ IDEA.
* Description:
* User: wjx
* Date: 2019-05-06
* Time: 19:12
*/
public class MainTest 
    public static void main(String[] args) 
        showInfo();
        TreesTest treesTest;
        treesTest = new TreesTest();
        showInfo();
        treesTest.display();
        showInfo();


    
    public static void showInfo()
        long max = Runtime.getRuntime().maxMemory();
        long total = Runtime.getRuntime().totalMemory();


        long free  = Runtime.getRuntime().totalMemory();


        long used = total - free;


        System.out.println("最大内存= "+max);
        System.out.println("已分配内存= "+ total);
        System.out.println("已分配剩余内存内存= "+free);
        System.out.println("已用内存= "+used);
        System.out.println("当前时间="+System.currentTimeMillis());
        System.out.println();




    

• 这些树之间有什么关系，大量的对象导致内存泄漏，如何将对象变少：
• 分成两种状态：

• 内部状态：可以公用的放在一起的 display()
• 外部状态：xCoord, yCoord, age

• 内部状态放到类里面
• 外部状态简化成一个树管理的类来管理外部状态
• 显示的时候使用外部状态在调用内部状态

• 代码分析：

package yingliangmoshi.TreeFlyWeight;


/**
* Created with IntelliJ IDEA.
* Description:
* User: wjx
* Date: 2019-05-06
* Time: 19:25
*/


/**
* 内部状态
*/
public class TreeFlyWeight 
    public TreeFlyWeight()


    
    //只放一个内部状态
    public void display(int xCoord, int yCoord, int age)
//        System.out.println(xCoord);
    

package yingliangmoshi.TreeFlyWeight;


/**
* Created with IntelliJ IDEA.
* Description:
* User: wjx
* Date: 2019-05-06
* Time: 19:26
*/


/**
* 处理外部状态
*/
public class TreeManager 
    public int length = 1000000;
    //将外部状态放到数组中
    int[] xArray = new int[length];
    int[] yArray = new int[length];
    int[] ageArray = new int[length];
    private TreeFlyWeight treeFlyWeight;
    public TreeManager()
        treeFlyWeight = 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++)
            treeFlyWeight.display(xArray[i], yArray[i], ageArray[i]);
        
    

package yingliangmoshi.TreeFlyWeight;


/**
* Created with IntelliJ IDEA.
* Description:
* User: wjx
* Date: 2019-05-06
* Time: 19:29
*/
public class MainTest 
    public static void main(String[] args) 
        showInfo();
        TreeManager treeManager;
        treeManager = new TreeManager();
        showInfo();
        treeManager.displayTrees();
        showInfo();
    
    public static void showInfo()
        long max = Runtime.getRuntime().maxMemory();
        long total = Runtime.getRuntime().totalMemory();


        long free  = Runtime.getRuntime().totalMemory();


        long used = total - free;


        System.out.println("最大内存= "+ max);
        System.out.println("已分配内存= "+ total);
        System.out.println("已分配剩余内存内存= "+ free);
        System.out.println("已用内存= " + used);
        System.out.println("当前时间="+System.currentTimeMillis());
        System.out.println();




    

• 不管项目变得多么复杂：

当存在多个细粒度对象的时候，找到公共方法，抽象成一个抽象类