有限BlockingQueue资源在多线程池ThreadPoolExector中的控制和处理

有时候我们需要处理类似这样的问题

1. 队列资源是有限的，一条队列里只能有10个位置，当满了后，后面来的需要等待前面的处理完有空位后再被处理。

2. 处理是多线程的，都在读这个队列

在不考滤第三方队列，单纯用JDK支持的BlockingQueue和ThreadPoolExecutor实现。可以是：

1.限制BQ的大小，每个新的item通过put放法放入BQ中,这个方法的意思是如果满了就会等空位

2.把BQ放到ThreadPoolExecutor中， 然后启动 threadPoolExecutor中的work去执行这些Runnable 

3.  需要调 用 prestartAllCoreThreads 来使线程work动作起来处理队列里的请求

下面是一个例子：

public class BlockingQueueTest {public static void main(String[] args) throws InterruptedException {BlockingQueue<Runnable> sharedQueue = new LinkedBlockingQueue<>(10); //capacityThreadPoolExecutor eService =  new ThreadPoolExecutor(3, 3,                0L, TimeUnit.MILLISECONDS,                sharedQueue);eService.prestartAllCoreThreads();for(int i=0;i<100;i++){System.out.println(" before current:"+i+",queue size:"+sharedQueue.size());Runnable task=()->{try {Thread.sleep(10);} catch (Exception e) {e.printStackTrace();}System.out.println(" queue size:"+sharedQueue.size());};sharedQueue.put(task);System.out.println(" after current:"+i+",queue size:"+sharedQueue.size());}eService.shutdown();}}

输出结果如果，可以看得出queue size最大就是10了，因为是用了put ：

 before current:0,queue size:0
 after current:0,queue size:1
 before current:1,queue size:0
 after current:1,queue size:1
 before current:2,queue size:0
 after current:2,queue size:0
 before current:3,queue size:0
 after current:3,queue size:1
 before current:4,queue size:1
 after current:4,queue size:2
 before current:5,queue size:2
 after current:5,queue size:3
 before current:6,queue size:3
 after current:6,queue size:4
 before current:7,queue size:4
 after current:7,queue size:5
 before current:8,queue size:5
 after current:8,queue size:6
 before current:9,queue size:6
 after current:9,queue size:7
 before current:10,queue size:7
 after current:10,queue size:8
 before current:11,queue size:8
 after current:11,queue size:9
 before current:12,queue size:9
 after current:12,queue size:10
 before current:13,queue size:10
 queue size:10
 queue size:10
 after current:13,queue size:10
 before current:14,queue size:9
 after current:14,queue size:10
 before current:15,queue size:10
 queue size:10
 after current:15,queue size:10
 before current:16,queue size:10
 queue size:10
 queue size:10
 queue size:10
 after current:16,queue size:10
 before current:17,queue size:8
 after current:17,queue size:9
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 after current:18,queue size:10
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 queue size:10
 queue size:10
 queue size:10
 after current:19,queue size:10
 before current:20,queue size:8
 after current:20,queue size:9
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 after current:21,queue size:10
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 queue size:10
 queue size:10
 queue size:10
 after current:22,queue size:9
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 after current:23,queue size:9
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 after current:24,queue size:10
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 queue size:10
 queue size:10
 after current:25,queue size:9
 queue size:10
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 after current:26,queue size:9
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 after current:27,queue size:10
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 queue size:10
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 after current:28,queue size:10
 before current:29,queue size:9
 after current:29,queue size:10
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 queue size:10
 after current:30,queue size:10
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 queue size:10
 queue size:10
 queue size:10
 after current:31,queue size:8
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 after current:32,queue size:9
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 after current:33,queue size:10
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 queue size:10
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 after current:34,queue size:10
 before current:35,queue size:8
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 after current:37,queue size:9
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 after current:43,queue size:10
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 queue size:10
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 after current:46,queue size:10
 before current:47,queue size:8
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 after current:48,queue size:10
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 after current:56,queue size:9
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 after current:57,queue size:10
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 after current:58,queue size:9
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 after current:59,queue size:10
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 after current:60,queue size:10
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 after current:61,queue size:10
 before current:62,queue size:8
 after current:62,queue size:9
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 after current:63,queue size:10
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 queue size:10
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 after current:64,queue size:10
 before current:65,queue size:8
 after current:65,queue size:9
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 after current:66,queue size:10
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 after current:67,queue size:9
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 after current:68,queue size:9
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 after current:69,queue size:10
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 queue size:0
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