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; }