Mega Code Archive
Java util concurrent ThreadPoolExecutor and thread pool
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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;
}
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