Android的 - 内存不足。

问题描述

我知道它是我应该只是谷歌，但也许你们能救我的某个时候。

我试着在我的Andr​​oid应用程序运行日志处理后的某个时候我得到了内存不足的exeption。

我想知道为什么它的发生？

 类LongOperation扩展的AsyncTask＆LT;字符串，太虚，字符串＆GT; {

    @覆盖
    保护字符串doInBackground（字符串... PARAMS）{
        INT系数= 59;
        INT factorSuperNum = 35;
        INT NUM;
        名单＆LT;整数GT; alreadyIn =新的ArrayList＆LT;整数GT;（）;
        StringBuilder的SB =新的StringBuilder（）;
        对于（INT J = 0; J＆LT; 5000000; J ++）{
         alreadyIn.clear（）;
         的for（int i = 0;我小于5;我++）{
                NUM =（int）的（1 +（的Math.random（）*因子）％因子）;
                而（alreadyIn.contains（NUM））
                    NUM =（int）的（1 +（的Math.random（）*因子）％因子）;

                alreadyIn.add（NUM）;
         }
        如果（j％100000 == 0）
            Log.i（SendEmail，J +）;

        NUM =（int）的（1 +（的Math.random（）* factorSuperNum）％factorSuperNum）;
        alreadyIn.add（NUM）;

         对于（INT finalNum：alreadyIn）{
             sb.append（finalNum +）;
         }
         sb.append（\ N）;
     }
        返回null;
    }
}
 

解决方案

这code是坏的这么多的情况下...

第一个（的Math.random（）*因子）％系数为什么要乘以由随机因素？你知道，随机％X 是坏？

第二OOME是因为你在每一次迭代中添加行的StringBuilder打完5M迭代至少需要10MB（5M * 20-40bytes）

THRID连续服用5的因素，您可以使用ArrayList的使用范围从1到因子和洗牌，并采取冷杉5 elments：

 进口的java.util。*;
进口的java.lang。*;
进口java.io. *;

类LOLOLOLOLOL
{
    静态最终诠释F = 59;
    静态最终诠释FSN = 35;
    静态最后的ArrayList＆LT;整数GT; range1toF =新的ArrayList＆LT;整数GT;（）;
    静态最终随机RND =新的随机（）;
    静态{
        的for（int i = 1; I＆LT; F;我++）
            range1toF.add（ⅰ）;
    }
    公共静态无效的主要（字串[] args）抛出java.lang.Exception的
    {
        最后的PrintStream PS =新的PrintStream（System.out的）; //或者从文件
        的for（int i = 0;我小于20;我++）{
            Collections.shuffle（range1toF，RND）;
            为（诠释J = 0; J＆小于5; J ++）{
                ps.print（range1toF.get（J））;
                ps.print（，）;
            }
            ps.println（rnd.nextInt（FSN  -  1）+ 1）;
        }
    }
}
 

I know its something i should just google, but maybe you guys can save me sometime.

I tried running a log process in my android app and after sometime i got a out of memory exeption.

I am trying to understand why did it happend?

class LongOperation  extends AsyncTask<String, Void, String> {

    @Override
    protected String doInBackground(String... params) {
        int factor = 59;
        int factorSuperNum = 35;
        int num;
        List<Integer> alreadyIn = new ArrayList<Integer>();
        StringBuilder sb = new StringBuilder();
        for (int j=0; j<5000000; j++){
         alreadyIn.clear();
         for(int i=0;i<5;i++){
                num = (int) (1 + (Math.random() * factor) % factor);
                while (alreadyIn.contains(num))
                    num = (int) (1 + (Math.random() * factor) % factor);

                alreadyIn.add(num);
         }
        if(j % 100000 == 0)
            Log.i("SendEmail", j + "" );

        num = (int) (1 + (Math.random() * factorSuperNum) % factorSuperNum);
        alreadyIn.add(num);

         for (int finalNum : alreadyIn) {
             sb.append(finalNum + " ");
         }
         sb.append("\n");
     }
        return null;
    }
}

解决方案

this code is bad at so many cases ...

first (Math.random() * factor) % factor why you are multiplying random by factor? do you know that random % x is bad?

second OOME is because you add line to StringBuilder in every iteration so after 5M iteration it takes at least 10MB (5M * 20-40bytes)

thrid for taking 5 from factor you can use ArrayList with range from 1 to factor and shuffle it and take firs 5 elments:

import java.util.*;
import java.lang.*;
import java.io.*;

class LOLOLOLOLOL
{
    static final int F = 59;
    static final int FSN = 35;
    static final ArrayList<Integer> range1toF = new ArrayList<Integer>();
    static final Random rnd = new Random();
    static{
        for(int i = 1; i < F; i++)
            range1toF.add(i);
    }
    public static void main (String[] args) throws java.lang.Exception
    {
        final PrintStream ps = new PrintStream(System.out); //or from File
        for(int i = 0; i < 20; i++){
            Collections.shuffle(range1toF, rnd);
            for(int j = 0; j< 5; j++){
                ps.print(range1toF.get(j));
                ps.print(", ");
            }
            ps.println(rnd.nextInt(FSN - 1) + 1);
        }
    }
}

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