Java 线程池内容，全在这里了

/**
* 1.未使用线程池
*/
public class ThreadDemo {
public static void main(String[] args) {
List<Integer> list = new LinkedList<Integer>();
long startTime = System.currentTimeMillis();
for (int i = 0; i < 100000; i++) {
new Thread(()->{
list.add(new Random().nextInt());
            }).start();
        }
long endTime = System.currentTimeMillis();
System.out.println("耗时:"+(endTime-startTime));
    }
}

/**
1. 2.使用线程池
*/
public class ThreadDemo {
public static void main(String[] args) {
ThreadPoolExecutor executor = new ThreadPoolExecutor(50, 1000,
0L, TimeUnit.SECONDS,
new LinkedBlockingQueue<Runnable>());

List<Integer> list = new LinkedList<Integer>();
long startTime = System.currentTimeMillis();
for (int i = 0; i < 100000; i++) {
executor.execute(new Thread(()->{
list.add(new Random().nextInt());
            }));
        }
//线程执行完成后,关闭线程池(此处仅为效果使用,开发用到不多)
executor.shutdown();
long endTime = System.currentTimeMillis();
System.out.println("耗时:"+(endTime-startTime));
    }
}

Fork/Join框架介绍

4.ThreadPoolExecutor 核心参数

public ThreadPoolExecutor(int corePoolSize,
int maximumPoolSize,
long keepAliveTime,
TimeUnit unit,
BlockingQueue<Runnable> workQueue,
ThreadFactory threadFactory,
RejectedExecutionHandler handler)

public static ExecutorService newSingleThreadExecutor() {
return new FinalizableDelegatedExecutorService
            (new ThreadPoolExecutor(1, 1,
0L, TimeUnit.MILLISECONDS,
new LinkedBlockingQueue<Runnable>()));
}

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

当然，可以重写线程工厂方法来修改线程名称

 ExecutorService pool = Executors.newFixedThreadPool(2, new ThreadFactory() {
private AtomicInteger t = new AtomicInteger(1);
@Override
public Thread newThread(Runnable r) {
return new Thread(r,"mypool_t"+t.getAndIncrement());
            }
        });

public static ExecutorService newCachedThreadPool() {
return new ThreadPoolExecutor(0, Integer.MAX_VALUE,
60L, TimeUnit.SECONDS,
new SynchronousQueue<Runnable>());
}

public static ExecutorService newWorkStealingPool() {
return new ForkJoinPool
        (Runtime.getRuntime().availableProcessors(),
ForkJoinPool.defaultForkJoinWorkerThreadFactory,
null, true);
}

​​Fork/join框架介绍​​

public static ScheduledExecutorService newScheduledThreadPool(int corePoolSize) {
return new ScheduledThreadPoolExecutor(corePoolSize);
}

public ScheduledThreadPoolExecutor(int corePoolSize) {
super(corePoolSize, Integer.MAX_VALUE, 0, NANOSECONDS,
new DelayedWorkQueue());
}

//1.以固定的频率
scheduledExecutor.scheduleAtFixedRate(() -> {
System.out.println("线程执行方法");
}, 0, 5, TimeUnit.SECONDS);

//2.以固定的延时
scheduledExecutor.scheduleWithFixedDelay(() -> {
System.out.println("线程执行方法");
}, 1, 5, TimeUnit.SECONDS);

public ScheduledFuture<?> scheduleAtFixedRate(Runnable command,
long initialDelay,
long period,
TimeUnit unit);

public ScheduledFuture<?> scheduleWithFixedDelay(Runnable command,
long initialDelay,
long delay,
TimeUnit unit);

public static ScheduledExecutorService newSingleThreadScheduledExecutor() {
return new DelegatedScheduledExecutorService
    (new ScheduledThreadPoolExecutor(1));
}

//拒绝策略使用(通过 new ThreadPoolExecutor.xxx 的方式引入)
ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(1, 1,
0L, TimeUnit.MILLISECONDS,
new LinkedBlockingQueue<Runnable>(), new ThreadPoolExecutor.AbortPolicy());

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