前言
做Android的這兩年時(shí)間，通過研究Android源碼，也會(huì)Java并發(fā)處理多線程有了自己的一些理解。
那么問題來了，如何實(shí)現(xiàn)一個(gè)串行的線程池呢？
思路
何為串行線程池呢？
也就是說，我們的Runnable對象應(yīng)該有個(gè)排隊(duì)的機(jī)制，它們順序從隊(duì)列尾部進(jìn)入，并且從隊(duì)列頭部選擇Runnable進(jìn)行執(zhí)行。
既然我們有了思路，那我們就考慮一下所需要的數(shù)據(jù)結(jié)構(gòu)？
既然是從隊(duì)列尾部插入Runnable對象，從隊(duì)列頭部執(zhí)行Runnable對象，我們自然需要一個(gè)隊(duì)列。Java的SDK已經(jīng)給我們提供了很好的隊(duì)列數(shù)據(jù)結(jié)構(gòu)，例如雙端隊(duì)列：ArrayDeque<Runnable>。
- 因?yàn)樯婕暗骄€程的執(zhí)行，那我們首先就需要有一個(gè)合適的線程池，使用ThreadPoolExecutor類即可構(gòu)造。
- 既然是串行執(zhí)行，那如何保持串行機(jī)制呢？我們可以通過try和finally機(jī)制，我們將傳入的Runnable對象重新封裝成一個(gè)新的Runnable對象，在新的Runnable的run方法的try塊中執(zhí)行Runnable的run方法，在finally中調(diào)用執(zhí)行隊(duì)列頭部Runnable對象出隊(duì)列，并放入線程池執(zhí)行的方法。
示例代碼
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import java.util.ArrayDeque;import java.util.concurrent.BlockingQueue;import java.util.concurrent.LinkedBlockingDeque;import java.util.concurrent.ThreadFactory;import java.util.concurrent.ThreadPoolExecutor;import java.util.concurrent.TimeUnit;import java.util.concurrent.atomic.AtomicInteger;/** * Created by wzy on 16-1-5. */public class SerialExecutor { private Runnable mActive; private ArrayDeque<Runnable> mArrayDeque = new ArrayDeque<>(); private static final int CPU_COUNT = Runtime.getRuntime().availableProcessors(); private static final int CORE_POOL_SIZE = CPU_COUNT + 1; private static final int MAXIMUM_POOL_SIZE = CPU_COUNT * 2 + 1; private static final int KEEP_ALIVE = 1; private static final BlockingQueue<Runnable> sPoolWorkQueue = new LinkedBlockingDeque<>(128); private static final ThreadFactory sThreadFactory = new ThreadFactory() { private final AtomicInteger mCount = new AtomicInteger(1); @Override public Thread newThread(Runnable r) { return new Thread(r, "Serial thread #" + mCount.getAndIncrement()); } }; private static final ThreadPoolExecutor THREAD_EXECUTOR = new ThreadPoolExecutor(CORE_POOL_SIZE, MAXIMUM_POOL_SIZE, KEEP_ALIVE, TimeUnit.SECONDS, sPoolWorkQueue, sThreadFactory); public synchronized void execute(final Runnable r) { mArrayDeque.offer(new Runnable() { @Override public void run() { try { r.run(); } finally { scheduleNext(); } } }); // 第一次入隊(duì)列時(shí)mActivie為空，因此需要手動(dòng)調(diào)用scheduleNext方法 if (mActive == null) { scheduleNext(); } } private void scheduleNext() { if ((mActive = mArrayDeque.poll()) != null) { THREAD_EXECUTOR.execute(mActive); } } public static void main(String[] args) { SerialExecutor serialExecutor = new SerialExecutor(); for (int i = 0; i < 10; i ++) { final int j = i; serialExecutor.execute(new Runnable() { @Override public void run() { System.out.println("The num is :" + (j + 1)); try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } } }); } }} |
執(zhí)行結(jié)果如下：
The num is :1
The num is :2
The num is :3
The num is :4
The num is :5
The num is :6
The num is :7
The num is :8
The num is :9
The num is :10
總結(jié)
以上就是本文關(guān)于Java并發(fā)之串行線程池實(shí)例解析的全部內(nèi)容，希望對大家有所幫助。感興趣的朋友可以繼續(xù)參閱本站其他相關(guān)專題，如有不足之處，歡迎留言指出。感謝朋友們對本站的支持！
原文鏈接：http://blog.csdn.net/wzy_1988/article/details/50461242
