Java 创建线程池的四种方式

1、newCachedThreadPool 创建一个可缓存线程池，如果线程池长度超过处理需要，可灵活回收空闲线程，若无可回收，则新建线程。

2、newFixedThreadPool 创建一个定长线程池，可控制线程最大并发数，超出的线程会在队列中等待。

3、newScheduledThreadPool 创建一个定长线程池，支持定时及周期性任务执行。

4、newSingleThreadExecutor 创建一个单线程化的线程池，它只会用唯一的工作线程来执行任务，保证所有任务按照指定顺序(FIFO, LIFO, 优先级)执行。

newCachedThreadPool

创建一个可缓存线程池，如果线程池长度超过处理需要，可灵活回收空闲线程，

若无可回收，则新建线程。

package cn.qbz.thread;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;public class Test111907 {    public static void main(String[] args) {        ExecutorService executorService = Executors.newCachedThreadPool();        for (int i = 0; i < 10; i++) {            final int temp = i;            executorService.execute(new Runnable() {                @Override                public void run() {                    try {                        Thread.sleep(1000);                    } catch (InterruptedException e) {                        e.printStackTrace();                    }                    System.out.println(Thread.currentThread().getName() + "   i=" + temp);                }            });        }    }}    public static ExecutorService newCachedThreadPool() {        return new ThreadPoolExecutor(0, Integer.MAX_VALUE,                                      60L, TimeUnit.SECONDS,                                      new SynchronousQueue<Runnable>());    }

newFixedThreadPool

创建一个定长线程池，可控制线程最大并发数，超出的线程会在队列中等待。

package cn.qbz.thread;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;public class Test111907 {    public static void main(String[] args) {        ExecutorService executorService = Executors.newFixedThreadPool(3);        for (int i = 0; i < 10; i++) {            final int temp = i;            executorService.execute(new Runnable() {                @Override                public void run() {                    try {                        Thread.sleep(100);                    } catch (InterruptedException e) {                        e.printStackTrace();                    }                    System.out.println(Thread.currentThread().getName() + "   i=" + temp);                }            });        }    }}    public static ExecutorService newFixedThreadPool(int nThreads) {        return new ThreadPoolExecutor(nThreads, nThreads,                                      0L, TimeUnit.MILLISECONDS,                                      new LinkedBlockingQueue<Runnable>());    }

newScheduledThreadPool

创建一个定长线程池，支持定时及周期性任务执行。

package cn.qbz.thread;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.ScheduledExecutorService;import java.util.concurrent.TimeUnit;public class Test111907 {    public static void main(String[] args) {        final long begin = System.currentTimeMillis();        ExecutorService executorService = Executors.newScheduledThreadPool(3);        for (int i = 0; i < 10; i++) {            final int temp = i;            final long time = begin;            executorService.schedule(new Runnable() {                @Override                public void run() {                    try {                        Thread.sleep(100);                    } catch (InterruptedException e) {                        e.printStackTrace();                    }                    System.out.println(Thread.currentThread().getName() + "   i=" + temp + "   time=" + (System.currentTimeMillis() - time));                }            }, 5, TimeUnit.SECONDS);        }    }}    public static ScheduledExecutorService newScheduledThreadPool(int corePoolSize) {        return new ScheduledThreadPoolExecutor(corePoolSize);    }    public ScheduledThreadPoolExecutor(int corePoolSize) {        super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS,              new DelayedWorkQueue());    }

newSingleThreadExecutor

创建一个单线程化的线程池，它只会用唯一的工作线程来执行任务，

保证所有任务按照指定顺序(FIFO, LIFO, 优先级)执行。

package cn.qbz.thread;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.ScheduledExecutorService;import java.util.concurrent.TimeUnit;public class Test111907 {    public static void main(String[] args) {        ExecutorService executorService = Executors.newSingleThreadExecutor();        for (int i = 0; i < 10; i++) {            final int temp = i;            executorService.execute(new Runnable() {                @Override                public void run() {                    try {                        Thread.sleep(100);                    } catch (InterruptedException e) {                        e.printStackTrace();                    }                    System.out.println(Thread.currentThread().getName() + "   i=" + temp);                }            });        }    }}

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