多线程编程_CountDownLatch同步倒数计数器

CountDownLatch是JAVA提供在java.util.concurrent包下的一个辅助类，可以把它看成是一个计数器，其内部维护着一个count计数，只不过对这个计数器的操作都是原子操作，同时只能有一个线程去操作这个计数器，CountDownLatch通过构造函数传入一个初始计数值，调用者可以通过调用CounDownLatch对象的cutDown()方法，来使计数减1；如果调用对象上的await()方法，那么调用者就会一直阻塞在这里，直到别人通过cutDown方法，将计数减到0，才可以继续执行。

利用这种性质可以做一些事情
简单举几种简单的例子
1.需要开多线程执行，等所有的执行完成之后。在做其他的事情。
2.某个线程执行的时间不确定，我想等5秒之后如果，如果线程还没执行完，处理其他的逻辑

1.需要开多线程执行，等所有的执行完成之后。在做其他的事情。

第一种可以模拟，赛跑比赛，每个运动员是一个线程。所有的线程到达终点比赛结束。

import java.util.concurrent.CountDownLatch;

public class Sample {
    /**
     * 计数器，用来控制线程
     * 传入参数2，表示计数器计数为2
     */
    private final static CountDownLatch mCountDownLatch = new CountDownLatch(2);

    /**
     * 示例工作线程类
     */
    private static class WorkingThread extends Thread {
        private final String mThreadName;
        private final int mSleepTime;
        public WorkingThread(String name, int sleepTime) {
            mThreadName = name;
            mSleepTime = sleepTime;
        }
        
        @Override
        public void run() {
            System.out.println("[" + mThreadName + "] started!");
            try {  
                    Thread.sleep(mSleepTime);  
            } catch (InterruptedException e) {  
                    e.printStackTrace();  
            }
            mCountDownLatch.countDown();
            System.out.println("[" + mThreadName + "] end!"); 
        }
    }
    
    /**
     * 示例线程类
     */
    private static class SampleThread extends Thread {
        
        @Override
        public void run() {
            System.out.println("[SampleThread] started!");
            try {
                // 会阻塞在这里等待 mCountDownLatch 里的count变为0；
                // 也就是等待另外的WorkingThread调用countDown()
                mCountDownLatch.await();
            } catch (InterruptedException e) {
                
            }
            System.out.println("[SampleThread] end!");
        }
    }
    
    public static void main(String[] args) throws Exception {
        // 最先run SampleThread
        new SampleThread().start();
        // 运行两个工作线程
        // 工作线程1运行5秒
        new WorkingThread("WorkingThread1", 5000).start();
        // 工作线程2运行2秒
        new WorkingThread("WorkingThread2", 2000).start();
    }
}

结果如下

[SampleThread] started!
[WorkingThread1] started!
[WorkingThread2] started!
[WorkingThread2] end!
[WorkingThread1] end!
[SampleThread] end!

2.某个线程执行的时间不确定，我想等2秒之后如果，如果线程还没执行完，处理其他的逻辑

               final CountDownLatch latch = new CountDownLatch(1);
                final File outFile = new File(dir, imageName);
                reuslt.path=outFile.getAbsolutePath();
                reuslt.bitmap=bitmap;
                Thread sleepThread = new Thread() {
                    @Override
                    public void run() {
                        super.run();
                        try {
                            Thread.sleep(2000);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                        reuslt.result=false;
                        reuslt.type=Reuslt.THREAD_SLEEP;
                        latch.countDown();
                    }
                };
                Thread saveThread = new Thread() {
                    @Override
                    public void run() {
                        super.run();
                       boolean result=BitmapUtils.saveBitmapWithQuality(bitmap, outFile.getPath(), picQuality);
                        reuslt.result=result;
                        reuslt.type=Reuslt.THREAD_SAVE;
                        latch.countDown();
                    }
                };

                sleepThread.start();
                saveThread.start();

                try {
                    latch.await();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
　　　　　　　　　　//TODO samethings

 public static List<List<ProcessInfo>> getRunningProcessListTheadPool(final Context context) {
        if (DEBUG) {
            Log.i(TAG, "getRunningProcessListTheadPool");
        }
        ActivityManager activityManager = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
        final PackageManager packageManager=context.getPackageManager();
        long time = 0l;
        if (DEBUG) {
            time = System.currentTimeMillis();
        }
        final CopyOnWriteArrayList<ProcessInfo> processList = new CopyOnWriteArrayList<ProcessInfo>();
        final ArrayList<ProcessInfo> whiteListProcess = new ArrayList<ProcessInfo>();
        List<List<ProcessInfo>> returnList = new ArrayList<List<ProcessInfo>>();
        returnList.add(processList);
        returnList.add(whiteListProcess);

        List<RunningAppProcessInfo> allRunningProcessesList = null;
        try {
            allRunningProcessesList = activityManager.getRunningAppProcesses();
        } catch (Exception e) {
            if (DEBUG) {
                Log.e(TAG, "系统出错 ActivityManager.getRunningAppProcesses Exception");
            }
        }

        //5.0以上有部分手机getRunningAppProcesses只能获得当前运行的自己的程序
        if (!BoostRunningProcessUtil.isRunningAppProcessesEnable(allRunningProcessesList)) {
            allRunningProcessesList = GetRunningProcessUtil.getRunningAppProcesses(activityManager, packageManager);
            if (DEBUG) {
                Log.e(TAG, "5.0以上有部分手机 打印获取的程序列表" );
                for(RunningAppProcessInfo item:allRunningProcessesList){
                    Log.i(TAG,item.processName);
                }
                Log.e(TAG, "5.0以上有部分手机getRunningAppProcesses只能获得当前运行的自己的程序=");
            }
        }

        if (allRunningProcessesList == null || allRunningProcessesList.isEmpty()) {
            return returnList;
        }

        List<RunningServiceInfo> runningServicesTemp = null;
        try {
            runningServicesTemp = activityManager.getRunningServices(500);
        } catch (Exception e) {
            //java.lang.NullPointerException: Attempt to read from field
            //'android.content.ComponentName com.android.server.am.ServiceRecord.name' on a null object reference
            //at android.os.Parcel.readException(Parcel.java:1546)
            //at android.os.Parcel.readException(Parcel.java:1493)
            // at android.app.ActivityManagerProxy.getServices(ActivityManagerNative.java:3068)
            if (DEBUG) {
                Log.e(TAG, "系统出错 ActivityManager.getRunningServices Exception");
            }
        }

        if (runningServicesTemp == null) {
            runningServicesTemp = new ArrayList<RunningServiceInfo>(0);
        }else{
            if (DEBUG) {
                Log.e(TAG, "获取到的运行的service size"+runningServicesTemp.size() );
                for(RunningServiceInfo item:runningServicesTemp){
                    Log.i(TAG,item.process);
                }
            }
        }

        final List<RunningServiceInfo> runningServices = runningServicesTemp;
        int size = allRunningProcessesList.size();
        // 开始的倒数锁
        final CountDownLatch begin = new CountDownLatch(1);
        // 结束的倒数锁
        final CountDownLatch end = new CountDownLatch(size);
        final ExecutorService exec = BoosterExecutorsPro.newFixedThreadPool("getRunningProcessListTheadPool",6);

        final List<String> mobiProducts = Arrays.asList(SysClearEnv.MOBIMAGICP_PRD);
        final String myPkg=context.getPackageName();
        for (RunningAppProcessInfo item : allRunningProcessesList) {
            //////////////////////////////////////////////////////////////////////
            final RunningAppProcessInfo runningAppProcessInfo = item;
            Runnable run = new Runnable() {
                public void run() {
                    try {
                        // 等待.如果当前计数为零，则此方法立即返回。
                        begin.await();

                        /*********************************************************************************/
                        if (runningAppProcessInfo == null) {
                            return;
                        }
                        final String processName = runningAppProcessInfo.processName;
                        if (TextUtils.isEmpty(processName)) {
                            return;
                        }

                        long singleStartTime = 0;
                        if (DEBUG) {
                            singleStartTime = System.currentTimeMillis();
                            Log.d(TAG, processName + " " + Arrays.toString(runningAppProcessInfo.pkgList)
                                    + " importance:" + runningAppProcessInfo.importance);
                        }
                     
                        // 获取进程相关的服务
                        String[] processServices = LoadProcessUtils.getProcessServices(processName, runningServices);

                        /*
                         * 由于 Android 系统中一个进程可能是由多个不同的包共享的，试过把这些包都显示出来，发现比如说设置的进程，里面包含了
                         * Status Bar，
                         * 设置，设置存储三个包，它们的图标都一样，用户就会提出疑问说为什么有三个一样的，没办法，后面就只显示其中一个包
                         * 进程中如果没有package，则默认可杀
                         */
                        String[] packageList = (runningAppProcessInfo.pkgList == null) ? new String[] { processName }
                                : runningAppProcessInfo.pkgList;

                        //根据PackageName处理
                        for (String packageName : packageList) {
                          
                            long time = System.currentTimeMillis();
                    
                            PackageInfo packageInfo = null;
                            try {
                                if (SysClearEnv.PACKAGE_CACHE) {
                                    packageInfo = getPackageInfo(packageManager, packageName);
                                } else {
                                    packageInfo = packageManager.getPackageInfo(packageName, 0);
                                }

                             
                                if (packageInfo != null) {
                                    if (!TextUtils.isEmpty(packageInfo.sharedUserId)) {
                                        flag = ConfigLoader.getInstance(context).queryFilter(
                                                ConfigLoader.SHARED_USER_ID, packageInfo.sharedUserId);
                                    }
                                 
                                }
                            } catch (Exception e) {
                                //NameNotFoundException, Package manager has died
                                if (DEBUG) {
                                    Log.e(TAG, "getPackageInfo", e);
                                }
                            }
                            ProcessInfo processInfo = LoadProcessUtils.createProcessInfo(context, packageInfo,
                                    runningAppProcessInfo, packageName, processName, processServices);


                            // 当应用有多个进程时，将每个进程内存累加；
                            boolean unAddFlag = true;
                            synchronized (processList) {
                                for (ProcessInfo existProcessInfo : processList) {
                                    if (packageName.equals(existProcessInfo.packageName)) {
                                        // 取最小的一个进程importance作为合并进程的importance// 修正读到的flag被合并后消失的情况// 合并服务// 合并PID
                                        unAddFlag = false;
                                        break;
                                    }
                                }

                                if (unAddFlag) {
                          
                                    processList.add(processInfo);
                                }
                            }
                        }

                     

                        /*********************************************************************************/
                    } catch (Exception e) {
                        if (DEBUG) {
                            Log.e(TAG, "====getRunningProcessList有误!!!!====", e);
                        }
                    } finally {
                        // 每个 线程执行完成end就减一
                        end.countDown();
                    }

                }
            };
            exec.submit(run);
            //////////////////////////////////////////////////////////////////////
        }
        // begin减一
        begin.countDown();
        // 等待结束
        try {
            end.await();
        } catch (Exception e) {
            
        }
        exec.shutdown();


        return returnList;
    }