ThreadPoolTest.java Source code

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Here is the source code for ThreadPoolTest.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.ArrayList;
import java.util.Scanner;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.ThreadPoolExecutor;

/**
 * @version 1.0 2004-08-01
 * @author Cay Horstmann
 */
public class ThreadPoolTest {
    public static void main(String[] args) throws Exception {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter base directory (e.g. /usr/local/jdk5.0/src): ");
        String directory = in.nextLine();
        System.out.print("Enter keyword (e.g. volatile): ");
        String keyword = in.nextLine();

        ExecutorService pool = Executors.newCachedThreadPool();

        MatchCounter counter = new MatchCounter(new File(directory), keyword, pool);
        Future<Integer> result = pool.submit(counter);

        try {
            System.out.println(result.get() + " matching files.");
        } catch (ExecutionException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
        }
        pool.shutdown();

        int largestPoolSize = ((ThreadPoolExecutor) pool).getLargestPoolSize();
        System.out.println("largest pool size=" + largestPoolSize);
    }
}

/**
 * This task counts the files in a directory and its subdirectories that contain
 * a given keyword.
 */
class MatchCounter implements Callable<Integer> {
    /**
     * Constructs a MatchCounter.
     * 
     * @param directory
     *          the directory in which to start the search
     * @param keyword
     *          the keyword to look for
     * @param pool
     *          the thread pool for submitting subtasks
     */
    public MatchCounter(File directory, String keyword, ExecutorService pool) {
        this.directory = directory;
        this.keyword = keyword;
        this.pool = pool;
    }

    public Integer call() {
        count = 0;
        try {
            File[] files = directory.listFiles();
            ArrayList<Future<Integer>> results = new ArrayList<Future<Integer>>();

            for (File file : files)
                if (file.isDirectory()) {
                    MatchCounter counter = new MatchCounter(file, keyword, pool);
                    Future<Integer> result = pool.submit(counter);
                    results.add(result);
                } else {
                    if (search(file))
                        count++;
                }

            for (Future<Integer> result : results)
                try {
                    count += result.get();
                } catch (ExecutionException e) {
                    e.printStackTrace();
                }
        } catch (InterruptedException e) {
        }
        return count;
    }

    /**
     * Searches a file for a given keyword.
     * 
     * @param file
     *          the file to search
     * @return true if the keyword is contained in the file
     */
    public boolean search(File file) {
        try {
            Scanner in = new Scanner(new FileInputStream(file));
            boolean found = false;
            while (!found && in.hasNextLine()) {
                String line = in.nextLine();
                if (line.contains(keyword))
                    found = true;
            }
            in.close();
            return found;
        } catch (IOException e) {
            return false;
        }
    }

    private File directory;

    private String keyword;

    private ExecutorService pool;

    private int count;
}