java中queue的使用 (二)
索线程个数
// 基于ArrayBlockingQueue的阻塞队列
BlockingQueue queue = new ArrayBlockingQueue(
FILE_QUEUE_SIZE);
//只启动一个线程来搜索目录
FileEnumerationTask enumerator = new FileEnumerationTask(queue,
new File(directory));
new Thread(enumerator).start();
//启动100个线程用来在文件中搜索指定的关键字
for (int i = 1; i <= SEARCH_THREADS; i++)
new Thread(new SearchTask(queue, keyword)).start();
}
}
class FileEnumerationTask implements Runnable {
//哑元文件对象，放在阻塞队列最后，用来标示文件已被遍历完
public static File DUMMY = new File("");
private BlockingQueue queue;
private File startingDirectory;
public FileEnumerationTask(BlockingQueue queue, File startingDirectory) {
this.queue = queue;
this.startingDirectory = startingDirectory;
}
public void run() {
try {
enumerate(startingDirectory);
queue.put(DUMMY);//执行到这里说明指定的目录下文件已被遍历完
} catch (InterruptedException e) {
}
}
// 将指定目录下的所有文件以File对象的形式放入阻塞队列中
public void enumerate(File directory) throws InterruptedException {
File[] files = directory.listFiles();
for (File file : files) {
if (file.isDirectory())
enumerate(file);
else
//将元素放入队尾，如果队列满，则阻塞
queue.put(file);
}
}
}
class SearchTask implements Runnable {
private BlockingQueue
queue;
private String keyword;
public SearchTask(BlockingQueue queue, String keyword) {
this.queue = queue;
this.keyword = keyword;
}
public void run() {
try {
boolean done = false;
while (!done) {
//取出队首元素，如果队列为空，则阻塞
File file = queue.take();
if (file == FileEnumerationTask.DUMMY) {
//取出来后重新放入，好让其他线程读到它时也很快的结束
queue.put(file);
done = true;
} else
search(file);
}
} catch (IOException e) {
e.printStackTrace();
} catch (InterruptedException e) {
}
}
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();
}
}