BlockingQueueTest.java Source code

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Here is the source code for BlockingQueueTest.java

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/*
   This program is a part of the companion code for Core Java 8th ed.
   (http://horstmann.com/corejava)
    
   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.
    
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
    
   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.Scanner;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;

/**
 * @version 1.0 2004-08-01
 * @author Cay Horstmann
 */
public class BlockingQueueTest {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter base directory (e.g. /usr/local/jdk1.6.0/src): ");
        String directory = in.nextLine();
        System.out.print("Enter keyword (e.g. volatile): ");
        String keyword = in.nextLine();

        final int FILE_QUEUE_SIZE = 10;
        final int SEARCH_THREADS = 100;

        BlockingQueue<File> queue = new ArrayBlockingQueue<File>(FILE_QUEUE_SIZE);

        FileEnumerationTask enumerator = new FileEnumerationTask(queue, new File(directory));
        new Thread(enumerator).start();
        for (int i = 1; i <= SEARCH_THREADS; i++)
            new Thread(new SearchTask(queue, keyword)).start();
    }
}

/**
 * This task enumerates all files in a directory and its subdirectories.
 */
class FileEnumerationTask implements Runnable {
    /**
     * Constructs a FileEnumerationTask.
     * @param queue the blocking queue to which the enumerated files are added
     * @param startingDirectory the directory in which to start the enumeration
     */
    public FileEnumerationTask(BlockingQueue<File> queue, File startingDirectory) {
        this.queue = queue;
        this.startingDirectory = startingDirectory;
    }

    public void run() {
        try {
            enumerate(startingDirectory);
            queue.put(DUMMY);
        } catch (InterruptedException e) {
        }
    }

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

    public static File DUMMY = new File("");

    private BlockingQueue<File> queue;
    private File startingDirectory;
}

/**
 * This task searches files for a given keyword.
 */
class SearchTask implements Runnable {
    /**
     * Constructs a SearchTask.
     * @param queue the queue from which to take files
     * @param keyword the keyword to look for
     */
    public SearchTask(BlockingQueue<File> queue, String keyword) {
        this.queue = queue;
        this.keyword = keyword;
    }

    public void run() {
        try {
            boolean done = false;
            while (!done) {
                File file = queue.take();
                if (file == FileEnumerationTask.DUMMY) {
                    queue.put(file);
                    done = true;
                } else
                    search(file);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
        }
    }

    /**
     * Searches a file for a given keyword and prints all matching lines.
     * @param file the file to search
     */
    public void search(File file) throws IOException {
        Scanner in = new Scanner(new FileInputStream(file));
        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);
        }
        in.close();
    }

    private BlockingQueue<File> queue;
    private String keyword;
}