線程池七大參數介紹

ExecutorService threadPool = Executors.newFixedThreadPool(5); 

public static ExecutorService newFixedThreadPool(int nThreads) { return new ThreadPoolExecutor(nThreads, nThreads, 0L, TimeUnit.MILLISECONDS, new LinkedBlockingQueue<Runnable>()); } 

public ThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue) { this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, Executors.defaultThreadFactory(), defaultHandler); } 

public ThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, ThreadFactory threadFactory, RejectedExecutionHandler handler) { if (corePoolSize < 0 || maximumPoolSize <= 0 || maximumPoolSize < corePoolSize || keepAliveTime < 0) throw new IllegalArgumentException(); if (workQueue == null || threadFactory == null || handler == null) throw new NullPointerException(); this.acc = System.getSecurityManager() == null ? null : AccessController.getContext(); this.corePoolSize = corePoolSize; this.maximumPoolSize = maximumPoolSize; this.workQueue = workQueue; this.keepAliveTime = unit.toNanos(keepAliveTime); this.threadFactory = threadFactory; this.handler = handler; } 

1. corePoolSize：線程池中常駐核心線程數
2. maximumPoolSize：線程池能夠容納同時執行的最大線程數，此值必須大於等於1，讀音[ˈmæksɪməm]咩西門-最大限度
3. keepAliveTime：多余的空閑線程存活時間。當前線程池數量超過corePoolSize時，當空閑時間到達keepAliveTime值時，多余空閑線程會被銷毀直到只剩下corePoolSize個線程為止。
4. unit：keepAliveTime的時間單位
5. workQueue：任務隊列，被提交但尚未執行的任務
6. threadFactory：表示生成線程池中的工作線程的線程工廠，用於創建線程，一般為默認線程工廠即可
7. handler：拒絕策略，表示當隊列滿了並且工作線程大於等於線程池的最大線程數（maximumPoolSize）時如何來拒絕來請求的Runnable的策略