android线程池的优化
16lz
2021-12-04
import java.io.IOException; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; public class Test { public static void main(String[] args) throws IOException, InterruptedException { ExecutorService service = Executors.newFixedThreadPool(2); for (int i = 0; i < 6; i++) { final int index = i; System.out.println("task: " + (i+1)); Runnable run = new Runnable() { @Override public void run() { System.out.println("thread start" + index); try { Thread.sleep(Long.MAX_VALUE); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println("thread end" + index); } }; service.execute(run); } } }
输出: task: 1
task: 2
thread start0
task: 3
task: 4
task: 5
task: 6
task: 7
thread start1
task: 8
task: 9
task: 10
task: 11
task: 12
task: 13
task: 14
task: 15
从实例可以看到for循环并没有被固定的线程池阻塞住,也就是说所有的线程task都被提交到了ExecutorService中,查看Executors.newFixedThreadPool()如下:
return new ThreadPoolExecutor(nThreads, nThreads,
0L, TimeUnit.MILLISECONDS,
new LinkedBlockingQueue<Runnable>());
}
可以看到task被提交都了LinkedBlockingQueue中。这里有个问题,如果任务列表很大,一定会把内存撑爆,如何解决?看下面:
import java.io.IOException; import java.util.concurrent.ArrayBlockingQueue; import java.util.concurrent.BlockingQueue; import java.util.concurrent.ThreadPoolExecutor; import java.util.concurrent.TimeUnit; public class Test { public static void main(String[] args) throws IOException, InterruptedException { BlockingQueue<Runnable> queue = new ArrayBlockingQueue<Runnable>(3); ThreadPoolExecutor executor = new ThreadPoolExecutor(3, 3, 1, TimeUnit.HOURS, queue, new ThreadPoolExecutor.CallerRunsPolicy()); for (int i = 0; i < 10; i++) { final int index = i; System.out.println("task: " + (index+1)); Runnable run = new Runnable() { @Override public void run() { System.out.println("thread start" + (index+1)); try { Thread.sleep(Long.MAX_VALUE); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println("thread end" + (index+1)); } }; executor.execute(run); } } }
task: 2
thread start1
task: 3
task: 4
task: 5
task: 6
task: 7
thread start2
thread start7
thread start6
线程池最大值为4(??这里我不明白为什么是设置值+1,即3+1,而不是3),准备执行的任务队列为3。可以看到for循环先处理4个task,然后把3个放到队列。这样就实现了自动阻塞队列的效果。记得要使用ArrayBlockingQueue这个队列,然后设置容量就OK了。
转载网址:http://heipark.iteye.com/blog/1393847
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