Java的List, Set, Map比較

首先我主要比較了
List: ArrayList, LinkedList
Set: HashSet, TreeSet
Map: HashMap, TreeMap
並且針對了這幾個新增刪除以及取得(Get)來做比較，測試方式是先新增10000個字串物件，然後刪除字串為"5000”的物件，再來則是利用while loop及foreach來展開全部的物件。
實驗環境為

CPU	Intel core i7 860 @2.80GHz
OS	WIndows 7 X86_64
MEM	6G
JDK	Java SE 6 Update 23

以下為數據結果:

	add(push)	delete(remove)	Get(foreach)	Get (while)
ArrayList	10	1	2	4
LinkedList	4	1	1	4
HashSet	13	0	2	5
TreeSet	38	0	4	6
HashMap	3	0	N/A	4
TreeMap	7	0	N/A	4

程式碼如下

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.TreeMap;
import java.util.TreeSet;


public class PerformanceTest {
 
 private static void ArrayListTest(int size){
  System.out.println("\nArrayListTest, Total size: "+size);
  ArrayList<String> list=new ArrayList<String>();
  long start=System.currentTimeMillis();
  for(int i=0;i<size;i++){
   list.add(Integer.toString(i));
  }
  System.out.println("1.Add time: "+(System.currentTimeMillis()-start)+" (ms)");
  
  start=System.currentTimeMillis();
  
   list.remove(Integer.toString(size/2));
  
  System.out.println("2.Delete time(delete the object "+size/2+") :"+(System.currentTimeMillis()-start)+" (ms)");
  
  start=System.currentTimeMillis();
  Iterator iterator = list.iterator();
  String s;
        while(iterator.hasNext()) {
         s=(String) iterator.next();
        }
  System.out.println("3.Get time(use iterator): "+(System.currentTimeMillis()-start)+" (ms)");
  
  start=System.currentTimeMillis();
  for(String i : list) {
   s=i;
        }
  System.out.println("4.Get time(use enhanced for loop): "+(System.currentTimeMillis()-start)+" (ms)");
 }
 
 private static void LinkedListTest(int size){
  System.out.println("\nLinkedListTest, Total size: "+size);
  LinkedList<String> list=new LinkedList<String>();
  long start=System.currentTimeMillis();
  for(int i=0;i<size;i++){
   list.add(Integer.toString(i));
  }
  System.out.println("1.Add time: "+(System.currentTimeMillis()-start)+" (ms)");
  
  start=System.currentTimeMillis();
  
   list.remove(Integer.toString(size/2));
  
  System.out.println("2.Delete time(delete the object "+size/2+") :"+(System.currentTimeMillis()-start)+" (ms)");
  
  start=System.currentTimeMillis();
  Iterator iterator = list.iterator();
  String s;
        while(iterator.hasNext()) {
         s=(String) iterator.next();
        }
  System.out.println("3.Get time(use iterator): "+(System.currentTimeMillis()-start)+" (ms)");
  
  start=System.currentTimeMillis();
  for(String i : list) {
   s=i;
        }
  System.out.println("4.Get time(use enhanced for loop): "+(System.currentTimeMillis()-start)+" (ms)");
 }
 
 private static void HashSetTest(int size){
  System.out.println("\nHashSetTest, Total size: "+size);
  HashSet<String> list=new HashSet<String>();
  long start=System.currentTimeMillis();
  for(int i=0;i<size;i++){
   list.add(Integer.toString(i));
  }
  System.out.println("1.Add time: "+(System.currentTimeMillis()-start)+" (ms)");
  
  start=System.currentTimeMillis();
  
   list.remove(Integer.toString(size/2));
  
   System.out.println("2.Delete time(delete the object "+size/2+") :"+(System.currentTimeMillis()-start)+" (ms)");
  
  start=System.currentTimeMillis();
  Iterator iterator = list.iterator();
  String s;
        while(iterator.hasNext()) {
         s=(String) iterator.next();
        }
  System.out.println("3.Get time(use iterator): "+(System.currentTimeMillis()-start)+" (ms)");
  
  start=System.currentTimeMillis();
  for(String i : list) {
   s=i;
        }
  System.out.println("4.Get time(use enhanced for loop): "+(System.currentTimeMillis()-start)+" (ms)");
 }
 
 private static void TreeSetTest(int size){
  System.out.println("\nTreeSetTest, Total size: "+size);
  TreeSet<String> list=new TreeSet<String>();
  long start=System.currentTimeMillis();
  for(int i=0;i<size;i++){
   list.add(Integer.toString(i));
  }
  System.out.println("1.Add time: "+(System.currentTimeMillis()-start)+" (ms)");
  
  start=System.currentTimeMillis();
  
   list.remove(Integer.toString(size/2));
  
   System.out.println("2.Delete time(delete the object "+size/2+") :"+(System.currentTimeMillis()-start)+" (ms)");
  
  start=System.currentTimeMillis();
  Iterator iterator = list.iterator();
  String s;
        while(iterator.hasNext()) {
         s=(String) iterator.next();
        }
  System.out.println("3.Get time(use iterator): "+(System.currentTimeMillis()-start)+" (ms)");
  
  start=System.currentTimeMillis();
  for(String i : list) {
   s=i;
        }
  System.out.println("4.Get time(use enhanced for loop): "+(System.currentTimeMillis()-start)+" (ms)");
 }
 
 private static void HashMapTest(int size){
  System.out.println("\nHashMapTest, Total size: "+size);
  HashMap<String,String> list=new HashMap<String,String>();
  long start=System.currentTimeMillis();
  for(int i=0;i<size;i++){
   list.put(Integer.toString(i),Integer.toString(i));
  }
  System.out.println("1.Add time: "+(System.currentTimeMillis()-start)+" (ms)");
  
  start=System.currentTimeMillis();
  
   list.remove(Integer.toString(size/2));
  
   System.out.println("2.Delete time(delete the object "+size/2+") :"+(System.currentTimeMillis()-start)+" (ms)");
  
  start=System.currentTimeMillis();
  Collection collection = list.values();
        Iterator iterator = collection.iterator();
        String s;
        while(iterator.hasNext()) {
            s=(String) iterator.next();
        }
  System.out.println("3.Get time(use iterator): "+(System.currentTimeMillis()-start)+" (ms)");
  
  
 }
 
 private static void TreeMapTest(int size){
  System.out.println("\nTreeMapTest, Total size: "+size);
  TreeMap<String,String> list=new TreeMap<String,String>();
  long start=System.currentTimeMillis();
  for(int i=0;i<size;i++){
   list.put(Integer.toString(i),Integer.toString(i));
  }
  System.out.println("1.Add time: "+(System.currentTimeMillis()-start)+" (ms)");
  
  start=System.currentTimeMillis();
  
   list.remove(Integer.toString(size/2));
  
   System.out.println("2.Delete time(delete the object "+size/2+") :"+(System.currentTimeMillis()-start)+" (ms)");
  
  start=System.currentTimeMillis();
  Collection collection = list.values();
        Iterator iterator = collection.iterator();
        String s;
        while(iterator.hasNext()) {
            s=(String) iterator.next();
        }
  System.out.println("3.Get time(use iterator): "+(System.currentTimeMillis()-start)+" (ms)");
  
  
 }
 public static void main(String[] args) {
  ArrayListTest(10000);
  LinkedListTest(10000);
  HashSetTest(10000);
  TreeSetTest(10000);
  HashMapTest(10000);
  TreeMapTest(10000);
 }
}

HDFS Performance Test

很久很久以前就想測測看了！測試的項目主要有:
1.使用fuse掛載HDFS然後測試使用cp上傳下載以及使用dd產生檔案的速度
2.使用command (hadoop dfs –get/-put )取得效能
過幾天再補一個使用HDFS API來寫檔的速度好了。
以下是測試結果:

我的結論是:1.在小檔案方面基本上可以以忽略的，誤差很大(因為檔案太小)
                    2.下載比上傳快(差異蠻大的)
                    3.使用fuse掛載會慢一點點
                    4..另外參考一個數值:兩台電腦使用scp傳輸1GB時間是23秒(43.5MB/s)

Ubuntu Software RAID 5

之前拿四顆硬碟分別是 Seagate的2T*1  1.5T*3，簡單測一下效能:
A.對照組:在其中一個1.5T的硬碟切一個266G的磁區格式化為EXT4
B.實驗組:把剩下的空間作成RAID5 所以有5.7T也是格式化為EXT4
實驗方式是以dd的指令來產生檔案，bs為512K，連續跑四次扣除最快和最慢的取平均。
         1K B          512KB              1MB            10MB             100MB            1GB              10GB
A   48.9MB/s    700.5MB/s      822.5/MB/s    1091MB/s      1700MB/s       45MB/s          46MB/s
B  22.2 MB/s     553 MB/s        787MB/s       1331MB/s      1700MB/s      363MB/s        120MB/s

簡單的結論: Softraid 5 在檔案超過10MB後寫入效能會比單顆硬碟好。

在Ubuntu解決使用lftp亂碼問題

lftp是一個很好用的工具，特別是對於我這個重度ftp的人！然而，有些人就是很喜歡使用Windows來架ftp偏偏又不支援utf-8.....結果lftp就亂碼了@@
解法是在登入後輸入:

set ftp:charset "big5"; set file:charset "utf-8"

就可以正確地顯示編碼了！

另外，介紹一下lftp:

登入: lftp user:pwd@site:port or lftp –u user site:port

我常用的指令除了cd 之外就是…mirror了!

mirror [-c 續傳] [-R 把本地mirror上去][-n 只下載新的檔案][-parallel=n 同時傳輸n個檔案] [remote 資料夾] [本地資料夾]

C2DM on Android 2.2

當測試C2DM的時候在Logcat看到這一行"emulatorUnable to start service Intent { act=com.google.android.c2dm.intent.REGISTER (has extras) }: not found"
解法是你的Android Emulator必須是使用Google APIs Add-On的版本!