[java多线程] - Thread&Runnable运用

　　负载是一个很大的话题，也是一个非常重要的话题。不管是在大的互联网软件中，还是在一般的小型软件，都对负载有一定的要求，负载过高会导致服务器压力过大；负载过低又比较浪费服务器资源，而且当高请求的时候还可能出现低效率的问题。多线程就是一种提高服务效率的方式。面对海量的用户请求，单线程肯定扛不住，那么多线程的需求也就应运而生，所以说掌握多线程的开发技术对于技术人员来说肯定是非常重要的。参考文档http://docs.oracle.com/javase/7/docs/api/。

---

一、Runnable使用

publicinterface Runnable {
   public abstract void run();
}

　　Runnable接口中，只有一个方法，就是run方法。该方法的主要作用是执行用户需要执行的代码。也就是说我们可以将我们需要在多线程环境下执行的代码放到run里面。

public class RunnableDemo {
    static SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

    public static void main(String[] args) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("子线程:" + Thread.currentThread().getName() + ":" + sdf.format(new Date()));
                try {
                    Thread.sleep(1000);// 休息1s
                } catch (InterruptedException e) {
                }
                System.out.println("子线程:" + Thread.currentThread().getName() + ":" + sdf.format(new Date()));
            }
        }).start();

        System.out.println("主线程:" + Thread.currentThread().getName() + ":" + sdf.format(new Date()));
    }
}

// 结果
/*
子线程:Thread-0:2015-08-27 18:25:14
主线程:main:2015-08-27 18:25:14
子线程:Thread-0:2015-08-27 18:25:15
*/

二、Thread使用

　　这个类是Java中的线程基础类，基本上多线程开发不管是直接或者间接均需要依赖上该类。主要介绍几个方法：

　　1、start方法： 该方法是线程执行入口，如果你需要你新建的线程开始执行，那么请调用start方法。

　　2、run方法：线程执行具体代码，放用户希望执行的代码。和start的区别是，调用start方法是使用多线程方法执行，如果调用run方法，那就是单线程执行。也就是说start方法是启动线程，run方法是执行具体代码。在上面的那个例子中，如果是调用run，而不是start方法，那么一定是先打印出来两个子线程的输出值，再打印主线程的输出值。

　　3、sleep方法：使当前线程休眠指定时间，参数为休眠的时间，单位毫秒。

　　4、interrupt方法： 中断线程的休眠(sleep, join等操作)，会产生InterruptedException异常。

public class InterruptThreadDemo {
    public static void main(String[] args) {
        Thread t1 = new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("子线程:" + Thread.currentThread().getName() + ":" + TimeUtil.nowTime());
                try {
                    Thread.sleep(2000); // 休息2s
                } catch (InterruptedException e) {
                    ThrowableUtil.logThrowable(e); // 打印异常
                }
                System.out.println("子线程:" + Thread.currentThread().getName() + ":" + TimeUtil.nowTime());
            }
        });
        t1.start();

        // 中断线程
        t1.interrupt();

        System.out.println("主线程:" + Thread.currentThread().getName() + ":" + TimeUtil.nowTime());
    }
}

InterruptThreadDemo

　　5、isAlive&isInterrupted&isDaemon方法：检测是否处于运行状态或者是否被中断或者判断是否守护模式运行。

　　 6、join方法：将其他线程的执行嵌入到当前线程中，等待嵌入线程执行完毕，该线程才会被唤醒进行执行。

public class JoinThreadDemo {
    public static void main(String[] args) {
        final Thread t1 = new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("子线程:" + Thread.currentThread().getName() + ":" + TimeUtil.nowTime());
                try {
                    Thread.sleep(5000); // 休息5s
                } catch (InterruptedException e) {
                    ThrowableUtil.logThrowable(e); // 打印异常
                }
                System.out.println("子线程:" + Thread.currentThread().getName() + ":" + TimeUtil.nowTime());
            }
        }, "1");
        Thread t2 = new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("子线程:" + Thread.currentThread().getName() + ":" + TimeUtil.nowTime());
                // 等待线程1执行完，再继续执行
                try {
                    t1.join();
                } catch (InterruptedException e) {
                    ThrowableUtil.logThrowable(e);
                }
                System.out.println("子线程:" + Thread.currentThread().getName() + ":" + TimeUtil.nowTime());
            }
        }, "2");
        t1.start();
        t2.start();

        System.out.println("主线程:" + Thread.currentThread().getName() + ":" + TimeUtil.nowTime());
    }
}

// 结果
/*
子线程:2:2015-08-27 18:52:29 457
主线程:main:2015-08-27 18:52:29 457
子线程:1:2015-08-27 18:52:29 457
子线程:1:2015-08-27 18:52:34 458
子线程:2:2015-08-27 18:52:34 458
*/

JoinThreadDemo

　　7、setDaemon方法：设置为守护模式，当主线程结束后，被设置为守护模式的线程自动结束。

　　8、currentThread方法：获取当前线程。

三、多线程的实际应用

　　多线程的应用是比较多的，比如说针对请求分别创建多个线程服务，下载等等。这里就弄一个下载美眉图片的小demo。

 import java.io.BufferedReader;
 import java.io.File;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.net.URL;
 import java.net.URLConnection;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
 import java.util.concurrent.LinkedBlockingDeque;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;

 import javax.imageio.stream.FileImageOutputStream;
 import javax.imageio.stream.ImageOutputStream;

 import com.gerry.bd.util.ThrowableUtil;

 public class BeautyGirlPhotoDownloadDemo {
     public static void main(String[] args) {
         String[] categorys = new String[] { "rihan", "yule", "dongm" };
         ConcurrentMap<String, BlockingQueue<String>> map = new ConcurrentHashMap<String, BlockingQueue<String>>();

         // 分别启用线程来获取图片的url
         for (String category : categorys) {
             BlockingQueue<String> queue = new LinkedBlockingDeque<>();
             map.put(category, queue); // 添加一个初始化
             Thread thread = new Thread(new FetchImageUrlRunnable(category, queue), "fetchimg_" + category);
             thread.start();
         }

         File imagePath = new File("D:/image/");
         // 每一个品类其两个线程去下载
         for (Map.Entry<String, BlockingQueue<String>> entry : map.entrySet()) {
             for (int i = 0; i < 2; i++) {
                 Thread thread = new Thread(new DownloadImageRunnable(imagePath, entry.getKey(), entry.getValue()), "downloadimage_" + entry.getKey() + i);
                 thread.start();
             }
         }
     }

     /**
      * 解析页面代码，保存图片url链接
      *
      * @author jsliuming
      *
      */
     public static class FetchImageUrlRunnable implements Runnable {
         private String category;
         private BlockingQueue<String> imageUrlQueue;

         public FetchImageUrlRunnable(String category, BlockingQueue<String> queue) {
             this.category = category;
             this.imageUrlQueue = queue;
         }

         @Override
         public void run() {
             try {
                 String url = "";
                 BufferedReader br = null;
                 for (int i = 10; i < 100; i++) {
                     for (int j = 1; j < 20; j++) {
                         url = "http://www.mm8mm8.com/" + this.category + "/list_" + i + "_" + j + ".html";
                         System.out.println(Thread.currentThread().getName() + ":" + url);

                         StringBuffer content = new StringBuffer();
                         try {
                             URLConnection connection = new URL(url).openConnection();
                             connection.connect();
                             br = new BufferedReader(new InputStreamReader(connection.getInputStream()));
                             String line = null;
                             while ((line = br.readLine()) != null) {
                                 content.append(line);
                             }
                         } catch (Exception e) {
                             ThrowableUtil.logThrowable(e);
                         } finally {
                             if (br != null) {
                                 try {
                                     br.close();
                                 } catch (Exception e) {
                                 }
                             }
                         }

                         // 已经拿到内容，开始解析url
                         if (content.length() == 0) {
                             // empty
                             break;
                         } else {
                             // 开始解析
                             for (String u : this.getHtmlImageUrlList(content.toString())) {
                                 this.imageUrlQueue.put(u);
                             }
                         }
                     }
                 }
             } catch (Throwable e) {
                 ThrowableUtil.logThrowable(e);
             }
         }

         /**
          * 获取图片url
          *
          * @param htmlText
          * @return
          */
         private List<String> getHtmlImageUrlList(String htmlText) {
             List<String> list = new ArrayList<String>();
             Pattern pattern = Pattern.compile("<img\\s*src\\s*=\\s*\"(?<imgUrl>[^\\s\"'<>]*)\"");
             Matcher matcher = pattern.matcher(htmlText);
             while (matcher.find()) {
                 list.add(matcher.group("imgUrl"));
             }
             return list;
         }
     }

     /**
      * 下载图片用线程
      *
      * @author jsliuming
      *
      */
     public static class DownloadImageRunnable implements Runnable {
         private String category;
         private BlockingQueue<String> imageUrlQueue;
         private File baseFile;

         public DownloadImageRunnable(File path, String category, BlockingQueue<String> queue) {
             this.category = category;
             this.imageUrlQueue = queue;
             baseFile = new File(path, this.category);
         }

         @Override
         public void run() {
             int index = 0;
             InputStream input = null;
             ImageOutputStream ios = null;
             while (true) {
                 try {
                     String imgurl = this.imageUrlQueue.take();

                     URLConnection connection = new URL(imgurl).openConnection();
                     connection.connect();
                     input = connection.getInputStream();
                     ios = new FileImageOutputStream(new File(baseFile, Thread.currentThread().getId() + "_" + index++ + ".jpg"));
                     byte[] buf = new byte[2048];
                     int n = -1;
                     while ((n = input.read(buf)) > 0) {
                         ios.write(buf, 0, n);
                     }
                 } catch (Throwable e) {
                     ThrowableUtil.logThrowable(e);
                 } finally {
                     if (input != null) {
                         try {
                             input.close();
                         } catch (Exception e) {
                         }
                     }
                     if (ios != null) {
                         try {
                             ios.close();
                         } catch (Exception e) {
                         }
                     }
                 }
             }
         }

     }
 }

BeautyGirlPhotoDownloadDemo .java

　　这个代码没有关闭的设置，所有在下载完成后，需要手动关闭。后期会改吧 。。。。。

===========================================================

使用CountDownLatch来控制下载线程下载完数据后结束程序，代码如下：

 import java.io.BufferedReader;
 import java.io.File;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.net.URL;
 import java.net.URLConnection;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.LinkedBlockingDeque;
 import java.util.concurrent.TimeUnit;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;

 import javax.imageio.stream.FileImageOutputStream;
 import javax.imageio.stream.ImageOutputStream;

 import com.gerry.bd.util.ThrowableUtil;

 public class BeautyGirlPhotoDownloadDemo {
     static volatile boolean fetchTheradRunning = true; // 用于控制结束线程
     static final CountDownLatch latch = new CountDownLatch(3); // 用于控制结束线程

     public static void main(String[] args) {
         String[] categorys = new String[] { "rihan", "yule", "dongm" };
         ConcurrentMap<String, BlockingQueue<String>> map = new ConcurrentHashMap<String, BlockingQueue<String>>();

         // 分别启用线程来获取图片的url
         for (String category : categorys) {
             BlockingQueue<String> queue = new LinkedBlockingDeque<>();
             map.put(category, queue); // 添加一个初始化
             Thread thread = new Thread(new FetchImageUrlRunnable(category, queue), "fetchimg_" + category);
             thread.start();
         }

         File imagePath = new File("D:/image/");
         // 每一个品类其两个线程去下载
         for (Map.Entry<String, BlockingQueue<String>> entry : map.entrySet()) {
             for (int i = 0; i < 2; i++) {
                 Thread thread = new Thread(new DownloadImageRunnable(imagePath, entry.getKey(), entry.getValue()), "downloadimage_" + entry.getKey() + i);
                 thread.start();
             }
         }

         new Thread(new Runnable() {
             @Override
             public void run() {
                 try {
                     latch.await();// 等待完成
                     fetchTheradRunning = false;
                 } catch (Throwable e) {
                     ThrowableUtil.logThrowable(e);
                 }
             }
         }).start();
     }

     /**
      * 解析页面代码，保存图片url链接
      *
      * @author jsliuming
      *
      */
     public static class FetchImageUrlRunnable implements Runnable {
         private String category;
         private BlockingQueue<String> imageUrlQueue;

         public FetchImageUrlRunnable(String category, BlockingQueue<String> queue) {
             this.category = category;
             this.imageUrlQueue = queue;
         }

         @Override
         public void run() {
             try {
                 String url = "";
                 BufferedReader br = null;
                 for (int i = 10; i < 1024; i++) {
                     for (int j = 1; j < 21; j++) {
                         url = "http://www.mm8mm8.com/" + this.category + "/list_" + i + "_" + j + ".html";
                         System.out.println(Thread.currentThread().getName() + ":" + url);

                         StringBuffer content = new StringBuffer();
                         try {
                             URLConnection connection = new URL(url).openConnection();
                             connection.connect();
                             br = new BufferedReader(new InputStreamReader(connection.getInputStream()));
                             String line = null;
                             while ((line = br.readLine()) != null) {
                                 content.append(line);
                             }
                         } catch (Exception e) {
                             ThrowableUtil.logThrowable(e);
                         } finally {
                             if (br != null) {
                                 try {
                                     br.close();
                                 } catch (Exception e) {
                                 }
                             }
                         }

                         // 已经拿到内容，开始解析url
                         if (content.length() == 0) {
                             // empty
                             break;
                         } else {
                             // 开始解析
                             for (String u : this.getHtmlImageUrlList(content.toString())) {
                                 this.imageUrlQueue.put(u);
                             }
                         }
                     }
                 }

                 // 完成后，通知
                 latch.countDown();
             } catch (Throwable e) {
                 ThrowableUtil.logThrowable(e);
             }
         }

         /**
          * 获取图片url
          *
          * @param htmlText
          * @return
          */
         private List<String> getHtmlImageUrlList(String htmlText) {
             List<String> list = new ArrayList<String>();
             Pattern pattern = Pattern.compile("<img\\s*src\\s*=\\s*\"(?<imgUrl>[^\\s\"'<>]*)\"");
             Matcher matcher = pattern.matcher(htmlText);
             while (matcher.find()) {
                 list.add(matcher.group("imgUrl"));
             }
             return list;
         }
     }

     /**
      * 下载图片用线程
      *
      * @author jsliuming
      *
      */
     public static class DownloadImageRunnable implements Runnable {
         private String category;
         private BlockingQueue<String> imageUrlQueue;
         private File baseFile;

         public DownloadImageRunnable(File path, String category, BlockingQueue<String> queue) {
             this.category = category;
             this.imageUrlQueue = queue;
             baseFile = new File(path, this.category);
         }

         @Override
         public void run() {
             int index = 0;
             InputStream input = null;
             ImageOutputStream ios = null;
             while (fetchTheradRunning || this.imageUrlQueue.size() > 0) {
                 try {
                     String imgurl = null;
                     while (true) {
                         imgurl = this.imageUrlQueue.poll(10, TimeUnit.SECONDS); // 阻塞10秒
                         if (imgurl != null || !fetchTheradRunning) {
                             break;
                         }
                     }
                     if (imgurl == null) { // 如果url为空，那么再次循环
                         continue;
                     }

                     URLConnection connection = new URL(imgurl).openConnection();
                     connection.connect();
                     input = connection.getInputStream();
                     ios = new FileImageOutputStream(new File(baseFile, Thread.currentThread().getId() + "_" + index++ + ".jpg"));
                     byte[] buf = new byte[2048];
                     int n = -1;
                     while ((n = input.read(buf)) > 0) {
                         ios.write(buf, 0, n);
                     }
                 } catch (Throwable e) {
                     ThrowableUtil.logThrowable(e);
                 } finally {
                     if (input != null) {
                         try {
                             input.close();
                         } catch (Exception e) {
                         }
                     }
                     if (ios != null) {
                         try {
                             ios.close();
                         } catch (Exception e) {
                         }
                     }
                 }
             }
         }
     }
 }

BeautyGirlPhotoDownloadDemo2