《java核心技術》第八版14.6節使用阻塞佇列的程式碼（生產者—消費者，根據關鍵字搜尋檔案內容）

package thread;

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

public class TestBlockingQueue {
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		System.out.print("輸入初始目錄：");
		String dir = in.nextLine();
		System.out.print("輸入要查詢的關鍵字：");
		String keyword = in.nextLine();
		
		final int QUEUE_SIZE = 100;
		final int THREAD_SIZE = 200;
		
		BlockingQueue<File> queue = new ArrayBlockingQueue<File>(QUEUE_SIZE);
		Thread enumeration = new Thread(new FileEnumerationTask(queue, new File(dir)));
		enumeration.start();
		List<Thread> threadList = new ArrayList<Thread>(THREAD_SIZE);
		for (int n=0; n<THREAD_SIZE; ++n) {
			Thread thread = new Thread(new SearchTask(queue, keyword));
			thread.start();
			threadList.add(thread);
		}
	}
}

class FileEnumerationTask implements Runnable {
	private BlockingQueue<File> queue;
	private File startingDir;
	public static final File DUMMY = new File("");

	// 構造器
	public FileEnumerationTask(BlockingQueue<File> queue, File startingDir) {
		this.queue = queue;
		this.startingDir = startingDir;
	}

	// 執行列舉的邏輯
	private void enumerate(File dir) throws InterruptedException {
		File[] files = dir.listFiles();
		for (File file : files) {
			if (file.isDirectory()) {
				enumerate(file);
			} else {
				queue.put(file); // 如果佇列滿，就阻塞。在阻塞時，如果本執行緒被中斷（interrupt），就會丟擲“中斷異常”。
			}
		}
	}

	@Override
	public void run() {
		try {
			enumerate(this.startingDir);
			queue.put(DUMMY);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}
}

class SearchTask implements Runnable {
	private BlockingQueue<File> queue;
	private String keyword;

	// 構造器
	public SearchTask(BlockingQueue<File> queue, String keyword) {
		this.queue = queue;
		this.keyword = keyword;
	}

	private 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);
			}
		}
	}

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