Java 创建线程池的四种方式

小灰灰 2020-06-11 14:27 938阅读 1赞

# 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。

```java
package cn.dandelioncloud.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());
}
```

**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。

```java
package cn.dandelioncloud.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());
}
```

**newScheduledThreadPool**

创建一个定长线程池，支持定时及周期性任务执行。

```java
package cn.dandelioncloud.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。