阿里规约中 并发处理 章节提到。
3、【强制】线程资源必须通过线程池提供，不允许在应用中自行显式创建线程。 说明：线程池的好处是减少在创建和销毁线程上所消耗的时间以及系统资源的开销，解决资源不足的问题。如果不使用线程池，有可能造成系统创建大量同类线程而导致消耗完内存或者“过度切换”的问题。
4、【强制】线程池不允许使用Executors去创建，而是通过ThreadPoolExecutor的方式，这样的处理方式让写的同学更加明确线程池的运行规则，规避资源耗尽的风险。
说明：Executors返回的线程池对象的弊端如下： 1） FixedThreadPool和SingleThreadPool：
允许的请求队列长度为Integer.MAX_VALUE，可能会堆积大量的请求，从而导致OOM。 2） CachedThreadPool：
允许的创建线程数量为Integer.MAX_VALUE，可能会创建大量的线程，从而导致OOM。
以下为工具类Executors，提供了简便创建线程池的方法。
Executors类创建线程池的方法，实际是调用ThreadPoolExecutor的构造方法。
public class Executors { public static ExecutorService newFixedThreadPool(int nThreads) { return new ThreadPoolExecutor(nThreads, nThreads, 0L, TimeUnit.MILLISECONDS, new linkedBlockingQueue()); } public static ExecutorService newFixedThreadPool(int nThreads, ThreadFactory threadFactory) { return new ThreadPoolExecutor(nThreads, nThreads, 0L, TimeUnit.MILLISECONDS, new linkedBlockingQueue(), threadFactory); } public static ExecutorService newSingleThreadExecutor() { return new FinalizableDelegatedExecutorService (new ThreadPoolExecutor(1, 1, 0L, TimeUnit.MILLISECONDS, new linkedBlockingQueue())); } public static ExecutorService newSingleThreadExecutor(ThreadFactory threadFactory) { return new FinalizableDelegatedExecutorService (new ThreadPoolExecutor(1, 1, 0L, TimeUnit.MILLISECONDS, new linkedBlockingQueue(), threadFactory)); } public static ExecutorService newCachedThreadPool() { return new ThreadPoolExecutor(0, Integer.MAX_VALUE, 60L, TimeUnit.SECONDS, new SynchronousQueue()); } public static ExecutorService newCachedThreadPool(ThreadFactory threadFactory) { return new ThreadPoolExecutor(0, Integer.MAX_VALUE, 60L, TimeUnit.SECONDS, new SynchronousQueue(), threadFactory); } public static ThreadFactory defaultThreadFactory() { return new DefaultThreadFactory(); }// 默认的线程池工厂，当不指定明确的时候，使用此类 private static class DefaultThreadFactory implements ThreadFactory { private static final AtomicInteger poolNumber = new AtomicInteger(1); private final ThreadGroup group; private final AtomicInteger threadNumber = new AtomicInteger(1); private final String namePrefix; DefaultThreadFactory() { SecurityManager s = System.getSecurityManager(); group = (s != null) ? s.getThreadGroup() : Thread.currentThread().getThreadGroup(); namePrefix = "pool-" + poolNumber.getAndIncrement() + "-thread-"; } public Thread newThread(Runnable r) { Thread t = new Thread(group, r, namePrefix + threadNumber.getAndIncrement(), 0); if (t.isDaemon()) t.setDaemon(false); if (t.getPriority() != Thread.NORM_PRIORITY) t.setPriority(Thread.NORM_PRIORITY); return t; } }
linkedBlockingQueue是默认使用的阻塞队列实现，linkedBlockingQueue初始化的部分代码
public class linkedBlockingQueue extends AbstractQueue implements BlockingQueue, java.io.Serializable { private final int capacity; public linkedBlockingQueue() { this(Integer.MAX_VALUE); } public linkedBlockingQueue(int capacity) { if (capacity <= 0) throw new IllegalArgumentException(); this.capacity = capacity; last = head = new Node(null); }}
阻塞队列初始化的容量过大，为 2的31次幂-1
public final class Integer extends Number implements Comparable {//@Native注解修饰成员变量，则表示这个变量可以被‘本地代码‘引用，常常被代码生成工具使用 @Native public static final int MAX_VALUE = 0x7fffffff;}