java多线程示例

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Java 多线程实例-测试多线程效率

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创建一个固定大小的txt文件

代码如下:
package test.multiThread;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;

publicclass FileCreate {
    privatefinalstatic String path = "C:\\Users\\Administrator\\Desktop\\test1.txt";
    privatefinalstatic String crlf=System.getProperty("line.separator");
    //单位是kb
    privatefinalstaticintsize = 1024*5; //5兆
    //是否限制文件大小
    privatestaticbooleanpsize = true;
    publicstaticvoid main(String[] args) throws IOException {
       File file = null; 
        OutputStream out = null; 
        if(psize){
        file = new File(path);
        int i=0;
        while(psize  && file.length()<= size*1024){
             out = new FileOutputStream(file,true);
             out = new FileOutputStream(file,true);
              out.write((String.valueOf(i)+"------").getBytes());
                out.write(crlf.getBytes());
                i++;
        }
        }else{
        file = new File(path);
        for (int i = 0; i <= 1500; i++) { 
              out = new FileOutputStream(file,true);
              out.write((String.valueOf(i)+"------").getBytes());
                out.write(crlf.getBytes());
            } 
        }
        if(null != out){
         out.flush();
             out.close(); 
        }
        file = null; 
        out = null;
      
    }
}




读取文件方法体，继承Runnable实现多线程

代码如下:
package test.multiThread;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

class MultiThread implements Runnable{  
    private static BufferedReader br = null; 
    private List<String> list; 
     
    static{ 
        try { 
            br = new BufferedReader(new FileReader("C:\\Users\\Administrator\\Desktop\\test1.txt"),3); 
        } catch (FileNotFoundException e) { 
            e.printStackTrace(); 
        } 
    } 
     
    public void run() { 
        String line = null; 
        int count = 0; 
        while(true) { 
            this.list = new ArrayList<String>(); 
            synchronized(br) { 
                try { 
                    while((line = br.readLine()) != null) { 
                        if(count<3) { 
                            list.add(line+Thread.currentThread().getName()); 
                            count++; 
                        }else { 
                                 list.add(line+Thread.currentThread().getName());
                            count = 0; 
                            break; 
                        } 
                    } 
                } catch (IOException e) { 
                    e.printStackTrace(); 
                } 
            } 
            try { 
                Thread.sleep(1); 
                display(this.list); 
            } catch (InterruptedException e) { 
                e.printStackTrace(); 
            } 
            if(line == null) 
                break; 
        } 
         
         
    } 
    /**
     * 打印读取的内容，不建议打印，影响效率
     */
    public void display(List<String> list) { 
        for(String str:list) { 
            System.out.println(str); 
        } 
        //System.out.println(list.size()); 
    } 
     
}

测试多线程效率
代码如下:
package test.multiThread;

import java.util.Date;

/** @author zongcai_liu
* @email   892530175@qq.com
* 2014-3-12 下午3:36:38
*/
publicclass ThreadReadDemo {
    publicstaticvoid main(String[] args) throws InterruptedException { 
       Date now = new Date();
       //线程数目
       int threadNum = 10;
       Thread[] thread = new Thread[threadNum];
       for(int i=0;i<thread.length;i++){
           thread[i] =  new Thread(new MultiThread(),String.valueOf(i));
           thread[i].start();
           //thread[i].join();
       }
       for(int i=0;i<thread.length;i++){
           while(thread[i].isAlive()){
            }
       }
        Date end = new Date();
       System.out.println("------线程时间---------");
        System.out.println((end.getTime()-now.getTime())/1000+"秒");
    } 
}













测试结果:

5M的txt文件

结果1：开启1个线程读取时间:
第一次:
<!--[if gte vml 1]><v:shapetype id="_x0000_t75"
coordsize="21600,21600" o:spt="75" o:preferrelative="t" path="m@4@5l@4@11@9@11@9@5xe"
filled="f" stroked="f">
<v:stroke joinstyle="miter"/>
<v:formulas>
  <v:f eqn="if lineDrawn pixelLineWidth 0"/>
  <v:f eqn="sum @0 1 0"/>
  <v:f eqn="sum 0 0 @1"/>
  <v:f eqn="prod @2 1 2"/>
  <v:f eqn="prod @3 21600 pixelWidth"/>
  <v:f eqn="prod @3 21600 pixelHeight"/>
  <v:f eqn="sum @0 0 1"/>
  <v:f eqn="prod @6 1 2"/>
  <v:f eqn="prod @7 21600 pixelWidth"/>
  <v:f eqn="sum @8 21600 0"/>
  <v:f eqn="prod @7 21600 pixelHeight"/>
  <v:f eqn="sum @10 21600 0"/>
</v:formulas>
<v:path o:extrusionok="f" gradientshapeok="t" o:connecttype="rect"/>
<o:lock v:ext="edit" aspectratio="t"/>
</v:shapetype><v:shape id="图片_x0020_1" o:spid="_x0000_i1032" type="#_x0000_t75"
alt="说明: C:\Users\Administrator\AppData\Roaming\Tencent\Users\892530175\QQ\WinTemp\RichOle\9AR($ZIR976%ISI39FN8I86.jpg"
style='width:157.5pt;height:32.25pt;visibility:visible;mso-wrap-style:square'>
<v:imagedata src="file:///C:\Users\ADMINI~1\AppData\Local\Temp\msohtmlclip1\01\clip_image001.jpg"
  o:title="9AR($ZIR976%ISI39FN8I86"/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]-->
第2次:
<!--[if gte vml 1]><v:shape
id="图片_x0020_2" o:spid="_x0000_i1031" type="#_x0000_t75" style='width:152.25pt;
height:45pt;visibility:visible;mso-wrap-style:square'>
<v:imagedata src="file:///C:\Users\ADMINI~1\AppData\Local\Temp\msohtmlclip1\01\clip_image002.png"
  o:title=""/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]-->


结果2：开启5个线程读取时间:
第一次:
<!--[if gte vml 1]><v:shape id="图片_x0020_5"
o:spid="_x0000_i1030" type="#_x0000_t75" style='width:167.25pt;height:51pt;
visibility:visible;mso-wrap-style:square'>
<v:imagedata src="file:///C:\Users\ADMINI~1\AppData\Local\Temp\msohtmlclip1\01\clip_image003.png"
  o:title=""/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]-->
第2次:
<!--[if gte vml 1]><v:shape
id="图片_x0020_6" o:spid="_x0000_i1029" type="#_x0000_t75" style='width:169.5pt;
height:52.5pt;visibility:visible;mso-wrap-style:square'>
<v:imagedata src="file:///C:\Users\ADMINI~1\AppData\Local\Temp\msohtmlclip1\01\clip_image004.png"
  o:title=""/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]-->

结果3：开启10个线程读取时间:
第一次:
<!--[if gte vml 1]><v:shape id="图片_x0020_9"
o:spid="_x0000_i1028" type="#_x0000_t75" style='width:150.75pt;height:45pt;
visibility:visible;mso-wrap-style:square'>
<v:imagedata src="file:///C:\Users\ADMINI~1\AppData\Local\Temp\msohtmlclip1\01\clip_image005.png"
  o:title=""/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]-->
第2次:
<!--[if gte vml 1]><v:shape
id="图片_x0020_10" o:spid="_x0000_i1027" type="#_x0000_t75" style='width:204.75pt;
height:56.25pt;visibility:visible;mso-wrap-style:square'>
<v:imagedata src="file:///C:\Users\ADMINI~1\AppData\Local\Temp\msohtmlclip1\01\clip_image006.png"
  o:title=""/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]-->

结果3：开启50个线程读取时间:
第一次:
<!--[if gte vml 1]><v:shape id="图片_x0020_13"
o:spid="_x0000_i1026" type="#_x0000_t75" style='width:192pt;height:62.25pt;
visibility:visible;mso-wrap-style:square'>
<v:imagedata src="file:///C:\Users\ADMINI~1\AppData\Local\Temp\msohtmlclip1\01\clip_image007.png"
  o:title=""/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]-->
第2次:
<!--[if gte vml 1]><v:shape
id="图片_x0020_14" o:spid="_x0000_i1025" type="#_x0000_t75" style='width:179.25pt;
height:93.75pt;visibility:visible;mso-wrap-style:square'>
<v:imagedata src="file:///C:\Users\ADMINI~1\AppData\Local\Temp\msohtmlclip1\01\clip_image008.png"
  o:title=""/>
</v:shape><![endif]--><!--[if !vml]--><!--[endif]-->