14.6 阻塞队列

import java.io.*;
import java.util.*;
import java.util.concurrent.*;

/**
 * @version 1.02 2015-06-21
 * @author Cay Horstmann
 */
public class BlockingQueueTest
{
   private static final int FILE_QUEUE_SIZE = 10;
   private static final int SEARCH_THREADS = 100;
   private static final File DUMMY = new File("");
   private static BlockingQueue<File> queue = new ArrayBlockingQueue<>(FILE_QUEUE_SIZE);

   public static void main(String[] args)
   {
      try (Scanner in = new Scanner(System.in)) 
      {
         System.out.print("Enter base directory (e.g. /opt/jdk1.8.0/src): ");
         String directory = in.nextLine();
         System.out.print("Enter keyword (e.g. volatile): ");
         String keyword = in.nextLine();

         Runnable enumerator = () -> {
            try
            {
               enumerate(new File(directory));
               queue.put(DUMMY);
            }
            catch (InterruptedException e)
            {
            }            
         };

         new Thread(enumerator).start();
         for (int i = 1; i <= SEARCH_THREADS; i++) {
            Runnable searcher = () -> {
               try
               {
                  boolean done = false;
                  while (!done)
                  {
                     File file = queue.take();
                     if (file == DUMMY)
                     {
                        queue.put(file);
                        done = true;
                     }
                     else search(file, keyword);
                  }
               }
               catch (IOException e)
               {
                  e.printStackTrace();
               }
               catch (InterruptedException e)
               {
               }               
            };
            new Thread(searcher).start();
         }
      }
   }

   /**
    * Recursively enumerates all files in a given directory and its subdirectories.
    * @param directory the directory in which to start
    */
   public static void enumerate(File directory) throws InterruptedException
   {
      File[] files = directory.listFiles();
      for (File file : files)
      {
         if (file.isDirectory()) enumerate(file);
         else queue.put(file);
      }
   }

   /**
    * Searches a file for a given keyword and prints all matching lines.
    * @param file the file to search
    * @param keyword the keyword to search for
    */
   public static void search(File file, String keyword) throws IOException
   {
      try (Scanner in = new Scanner(file, "UTF-8"))
      {
         int lineNumber = 0;
         while (in.hasNextLine())
         {
            lineNumber++;
            String line = in.nextLine();
            if (line.contains(keyword)) 
               System.out.printf("%s:%d:%s%n", file.getPath(), lineNumber, line);
         }
      }
   }
}