盧偉冰長文解析K60至尊版 對(duì)Redmi有著里程碑式的意義
在今天的Redmi后性能時(shí)代戰(zhàn)略發(fā)布會(huì)結(jié)束之后，Redmi總經(jīng)理盧偉冰又帶來了一篇長文，詳解了為什么 Redmi 要開啟后性能時(shí)代？為什么選擇和 MediaTek、Pixelworks 深度合作？以及后性
線程池七大核心參數(shù)如下所示:
public ThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, ThreadFactory threadFactory, RejectedExecutionHandler handler )1: 任務(wù)在提交的時(shí)候，首先判斷核心線程數(shù)是否已滿，如果沒有滿則直接添加到工作線程執(zhí)行
2: 如果核心線程數(shù)滿了，則判斷阻塞隊(duì)列是否已滿，如果沒有滿，當(dāng)前任務(wù)存入阻塞隊(duì)列
3：如果阻塞隊(duì)列也滿了，則判斷線程數(shù)是否小于最大線程數(shù)，如果滿足條件，則使用臨時(shí)線程執(zhí)行任務(wù)如果核心或臨時(shí)線程執(zhí)行完成任務(wù)后會(huì)檢查阻塞隊(duì)列中是否有需要執(zhí)行的線程，如果有，則使用非核心線程執(zhí)行任務(wù)
4:如果所有線程都在忙著（核心線程+臨時(shí)線程），則走拒絕策略
1.AbortPolicy：直接拋出異常，默認(rèn)策略
2.CallerRunsPolicy：用調(diào)用者所在的線程來執(zhí)行任務(wù)
3.DiscardOldestPolicy：丟棄阻塞隊(duì)列中靠最前的任務(wù)，并執(zhí)行當(dāng)前任務(wù)
4.DiscardPolicy：直接丟棄任務(wù)
案例:
public class TestThreadPoolExecutor { static class MyTask implements Runnable { private final String name; private final long duration; public MyTask(String name) { this(name, 0); } public MyTask(String name, long duration) { this.name = name; this.duration = duration; } @Override public void run() { try { LoggerUtils.get("myThread").debug("running..." + this); Thread.sleep(duration); } catch (InterruptedException e) { e.printStackTrace(); } } @Override public String toString() { return "MyTask(" + name + ")"; } } public static void main(String[] args) throws InterruptedException { AtomicInteger c = new AtomicInteger(1); ArrayBlockingQueue<Runnable> queue = new ArrayBlockingQueue<>(2); ThreadPoolExecutor threadPool = new ThreadPoolExecutor( 2, 3, 0, TimeUnit.MILLISECONDS, queue, r -> new Thread(r, "myThread" + c.getAndIncrement()), new ThreadPoolExecutor.AbortPolicy()); showState(queue, threadPool); threadPool.submit(new MyTask("1", 3600000)); showState(queue, threadPool); threadPool.submit(new MyTask("2", 3600000)); showState(queue, threadPool); threadPool.submit(new MyTask("3")); showState(queue, threadPool); threadPool.submit(new MyTask("4")); showState(queue, threadPool); threadPool.submit(new MyTask("5",3600000)); showState(queue, threadPool); threadPool.submit(new MyTask("6")); showState(queue, threadPool); } private static void showState(ArrayBlockingQueue<Runnable> queue, ThreadPoolExecutor threadPool) { try { Thread.sleep(300); } catch (InterruptedException e) { e.printStackTrace(); } List<Object> tasks = new ArrayList<>(); for (Runnable runnable : queue) { try { Field callable = FutureTask.class.getDeclaredField("callable"); callable.setAccessible(true); Object adapter = callable.get(runnable); Class<?> clazz = Class.forName("java.util.concurrent.Executors$RunnableAdapter"); Field task = clazz.getDeclaredField("task"); task.setAccessible(true); Object o = task.get(adapter); tasks.add(o); } catch (Exception e) { e.printStackTrace(); } } LoggerUtils.main.debug("pool size: {}, queue: {}", threadPool.getPoolSize(), tasks); }}workQueue: 當(dāng)沒有空閑核心線程時(shí)，新來任務(wù)會(huì)加入到此隊(duì)列排隊(duì)，隊(duì)列滿會(huì)創(chuàng)建救急線程執(zhí)行任務(wù)。
比較常見的有4個(gè)，用的最多是ArrayBlockingQueue和LinkedBlockingQueue。
inkedBlockingQueue** | ArrayBlockingQueue |
默認(rèn)無界，支持有界 | 強(qiáng)制有界 |
底層是鏈表 | 底層是數(shù)組 |
是懶惰的，創(chuàng)建節(jié)點(diǎn)的時(shí)候添加數(shù)據(jù) | 提前初始化 Node 數(shù)組 |
入隊(duì)會(huì)生成新 Node | Node需要是提前創(chuàng)建好的 |
兩把鎖（頭尾） | 一把鎖 |
左邊是LinkedBlockingQueue加鎖的方式，右邊是ArrayBlockingQueue加鎖的方式
在java.util.concurrent.Executors類中提供了大量創(chuàng)建連接池的靜態(tài)方法，常見就有四種
1.創(chuàng)建使用固定線程數(shù)的線程池
public static ExecutorService newFixedThreadPool(int nThreads) { return new ThreadPoolExecutor(nThreads, 0L, TimeUnit.MILLISECONDS, new LinkedBlockingQueue<>()); }/** * @author springboot葵花寶典 * @description: TODO */public class FixedThreadPoolTest { static class FixedThreadDemo implements Runnable{ @Override public void run() { String name = Thread.currentThread().getName(); for (int i = 0; i < 2; i++) { System.out.println(name + ":" + i); } } } public static void main(String[] args) throws InterruptedException { //創(chuàng)建一個(gè)固定大小的線程池，核心線程數(shù)和最大線程數(shù)都是3 ExecutorService executorService = Executors.newFixedThreadPool(3); for (int i = 0; i < 5; i++) { executorService.submit(new FixedThreadDemo()); Thread.sleep(10); } executorService.shutdown(); }}2.單線程化的線程池，它只會(huì)用唯一的工作線程來執(zhí)行任 務(wù)，保證所有任務(wù)按照指定順序(FIFO)執(zhí)行
public static ExecutorService newSingleThreadExecutor() { return new FinalizableDelegatedExecutorService (new ThreadPoolExecutor(1, 1, 0L, TimeUnit.MILLISECONDS, new LinkedBlockingQueue<>())); }/** * @author springboot葵花寶典 * @description: TODO */public class NewSingleThreadTest { static int count = 0; static class Demo implements Runnable { @Override public void run() { count++; System.out.println(Thread.currentThread().getName() + ":" + count); } } public static void main(String[] args) throws InterruptedException { //單個(gè)線程池，核心線程數(shù)和最大線程數(shù)都是1 ExecutorService exec = Executors.newSingleThreadExecutor(); for (int i = 0; i < 10; i++) { exec.execute(new Demo()); Thread.sleep(5); } exec.shutdown(); }}public static ExecutorService newCachedThreadPool() { return new ThreadPoolExecutor(0, Integer.MAX_VALUE, 60L, TimeUnit.SECONDS, n ew SynchronousQueue<>()); }/** * @author springboot葵花寶典 * @description: TODO */public class CachedThreadPoolTest { static class Demo implements Runnable { @Override public void run() { String name = Thread.currentThread().getName(); try { //修改睡眠時(shí)間，模擬線程執(zhí)行需要花費(fèi)的時(shí)間 Thread.sleep(100); System.out.println(name + "執(zhí)行完了"); } catch (InterruptedException e) { e.printStackTrace(); } } } public static void main(String[] args) throws InterruptedException { //創(chuàng)建一個(gè)緩存的線程，沒有核心線程數(shù)，最大線程數(shù)為Integer.MAX_VALUE ExecutorService exec = Executors.newCachedThreadPool(); for (int i = 0; i < 10; i++) { exec.execute(new Demo()); Thread.sleep(1); } exec.shutdown(); }}public ScheduledThreadPoolExecutor(int corePoolSize, ThreadFactory threadFactory, RejectedExecutionHandler handler{ super(corePoolSize, Integer.MAX_VALUE, 0, NANOSECONDS, new DelayedWorkQueue(), threadFactory, handler); }/** * @author springboot葵花寶典 * @description: TODO */public class ScheduledThreadPoolTest { static class Task implements Runnable { @Override public void run() { try { String name = Thread.currentThread().getName(); System.out.println(name + ", 開始：" + new Date()); Thread.sleep(1000); System.out.println(name + ", 結(jié)束：" + new Date()); } catch (InterruptedException e) { e.printStackTrace(); } } } public static void main(String[] args) throws InterruptedException { //按照周期執(zhí)行的線程池，核心線程數(shù)為2，最大線程數(shù)為Integer.MAX_VALUE ScheduledExecutorService scheduledThreadPool = Executors.newScheduledThreadPool(2); System.out.println("程序開始：" + new Date()); /** * schedule 提交任務(wù)到線程池中 * 第一個(gè)參數(shù)：提交的任務(wù) * 第二個(gè)參數(shù)：任務(wù)執(zhí)行的延遲時(shí)間 * 第三個(gè)參數(shù)：時(shí)間單位 */ scheduledThreadPool.schedule(new Task(), 0, TimeUnit.SECONDS); scheduledThreadPool.schedule(new Task(), 1, TimeUnit.SECONDS); scheduledThreadPool.schedule(new Task(), 5, TimeUnit.SECONDS); Thread.sleep(5000); // 關(guān)閉線程池 scheduledThreadPool.shutdown(); }}候選人：
在線程池中一共有7個(gè)核心參數(shù)：
在拒絕策略中又有4中拒絕策略
候選人：
首先判斷線程池里的核心線程是否都在執(zhí)行任務(wù)，如果不是則創(chuàng)建一個(gè)新的工作線程來執(zhí)行任務(wù)。如果核心線程都在執(zhí)行任務(wù)，則線程池判斷工作隊(duì)列是否已滿，如果工作隊(duì)列沒有滿，則將新提交的任務(wù)存儲(chǔ)在這個(gè)工作隊(duì) 列里。如果工作隊(duì)列滿了，則判斷線程池里的線程是否都處于工作狀態(tài)，如果沒有，則創(chuàng)建一個(gè)新的工作線程來執(zhí)行任 務(wù)。如果已經(jīng)滿了，則交給拒絕策略來處理這個(gè)任務(wù)。
候選人：
在jdk中默認(rèn)提供了4中方式創(chuàng)建線程池
本文鏈接：http://www.www897cc.com/showinfo-26-35298-0.html說一下線程池的核心參數(shù)，線程池的執(zhí)行原理
聲明：本網(wǎng)頁內(nèi)容旨在傳播知識(shí)，若有侵權(quán)等問題請(qǐng)及時(shí)與本網(wǎng)聯(lián)系，我們將在第一時(shí)間刪除處理。郵件：2376512515@qq.com
上一篇： 比亞迪面試，全程八股！
Copyright ? 2016-2023 天津谷騏科技有限公司 版權(quán)所有 sitemap.xml
違法及侵權(quán)請(qǐng)聯(lián)系：2376512515@qq.com 津ICP備18001702號(hào)
津公網(wǎng)安備 12010102000574號(hào)