JDK1.5的新功能_BlockingQueue（阻塞队列）
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转载：http://www.360doc.com/content/11/0104/08/3198380_83781542.shtml
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阻塞队列。该类主要提供了两个方法put()和take()，前者将一个对象放到队列中，如果队列已经满了，就等待直到有空闲节点；后者从head取一个对象，如果没有对象，就等待直到有可取的对象。
下面的例子比较简单，一个读线程，用于将要处理的文件对象添加到阻塞队列中，另外四个写线程用于取出文件对象，为了模拟写操作耗时长的特点，特让线程睡眠一段随机长度的时间。另外，该Demo也使用到了线程池和原子整型（AtomicInteger），AtomicInteger可以在并发情况下达到原子化更新，避免使用了synchronized，而且性能非常高。由于阻塞队列的put和take操作会阻塞，为了使线程退出，特在队列中添加了一个“标识”，算法中也叫“哨兵”，当发现这个哨兵后，写线程就退出。
当然线程池也要显式退出了。
package?concurrent;
import?java.io.File;
import?java.io.FileFilter;
import?java.util.concurrent.BlockingQueue;
import?java.util.concurrent.ExecutorService;
import?java.util.concurrent.Executors;
import?java.util.concurrent.LinkedBlockingQueue;
import?java.util.concurrent.atomic.AtomicInteger;
public?class?TestBlockingQueue?{
??static?long?randomTime()?{
????return?(long)?(Math.random()?*?1000);
??}
??public?static?void?main(String[]?args)?{
????//?能容纳100个文件
????final?BlockingQueue<File>?queue?=?new?LinkedBlockingQueue<File>(100);
????//?线程池
????final?ExecutorService?exec?=?Executors.newFixedThreadPool(5);
????final?File?root?=?new?File("F:\\JavaLib");
????//?完成标志
????final?File?exitFile?=?new?File("");
????//?读个数
????final?AtomicInteger?rc?=?new?AtomicInteger();
????//?写个数
????final?AtomicInteger?wc?=?new?AtomicInteger();
????//?读线程
????Runnable?read?=?new?Runnable()?{
??????public?void?run()?{
????????scanFile(root);
????????scanFile(exitFile);
??????}
??????public?void?scanFile(File?file)?{
????????if?(file.isDirectory())?{
??????????File[]?files?=?file.listFiles(new?FileFilter()?{
????????????public?boolean?accept(File?pathname)?{
??????????????return?pathname.isDirectory()
??????????????????||?pathname.getPath().endsWith(".java");
????????????}
??????????});
??????????for?(File?one?:?files)
????????????scanFile(one);
????????}?else?{
??????????try?{
????????????int?index?=?rc.incrementAndGet();
????????????System.out.println("Read0:?"?+?index?+?"?"
????????????????+?file.getPath());
????????????queue.put(file);
??????????}?catch?(InterruptedException?e)?{
??????????}
????????}
??????}
????};
????exec.submit(read);
????//?四个写线程
????for?(int?index?=?0;?index?<?4;?index++)?{
??????//?write?thread
??????final?int?NO?=?index;
??????Runnable?write?=?new?Runnable()?{
????????String?threadName?=?"Write"?+?NO;
????????public?void?run()?{
??????????while?(true)?{
????????????try?{
??????????????Thread.sleep(randomTime());
??????????????int?index?=?wc.incrementAndGet();
??????????????File?file?=?queue.take();
??????????????//?队列已经无对象
??????????????if?(file?==?exitFile)?{
????????????????//?再次添加"标志"，以让其他线程正常退出
????????????????queue.put(exitFile);
????????????????break;
??????????????}
??????????????System.out.println(threadName?+?":?"?+?index?+?"?"
??????????????????+?file.getPath());
????????????}?catch?(InterruptedException?e)?{
????????????}
??????????}
????????}
??????};
??????exec.submit(write);
????}
????exec.shutdown();
??}
}
