Java BblockingQueue和synchronized加锁关键字两种方法实现递归搜索文件关键字 用于衡量两种方法执行效率不准确，因为存在多线程，导致得出的时间不是正确的。

BlockingQueueTest.java

package chapter14.blockingQueue;

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

public class BlockingQueueTest {

    private static final int FILE_QUEUE_SIZE = 10;
    private static final int SEARCH_THREADS = 100;
    private static final File DUMMY = new File("");
    private static BlockingQueue<File> queue = new ArrayBlockingQueue<>(FILE_QUEUE_SIZE);

    public static void main(String[] args) {
        long startTime = System.currentTimeMillis();
        try (Scanner in = new Scanner(System.in)){
            System.out.print("Enter base directory (e.g. /opt/jdk1.8.0/src): ");
            String dir = in.nextLine();
            System.out.print("Enter keyword: ");
            String key = in.nextLine();

            Runnable enumerator = () -> {
                try {
                    enumerate(new File(dir));
                    queue.put(DUMMY);
                }catch (InterruptedException e){

                }
            };

            new Thread(enumerator).start();

            for(int i=1 ; i <= SEARCH_THREADS; i++){
                Runnable searcher = () -> {
                    try{
                        boolean done = false;
                        while (!done){
                            File file = queue.take();
                            if (file == DUMMY){
                                queue.put(file);
                                done = true;
                            }else search(file,key);
                        }
                    }catch (IOException e){

                    }
                    catch (InterruptedException e){

                    }
                };

                new Thread(searcher).start();
            }
        }
        long endTime = System.currentTimeMillis();

        System.out.println("耗时："+(endTime-startTime));
    }

    private static void search(File file, String key) throws IOException {
        try(Scanner in = new Scanner(file,"UTF-8")){
            int lineNumber = 0 ;
            while (in.hasNextLine()){
                lineNumber++;
                String line = in.nextLine();
                if (line.contains(key)) System.out.printf("%s:%d:%s:%n",file.getPath(),lineNumber,line);
            }
        }
    }

    private static void enumerate(File dir) throws InterruptedException {
        File[] files = dir.listFiles();
        for (File file : files){
            if (file.isDirectory()) enumerate(file);
            else queue.put(file);
        }
    }
}

LockTest.java

package chapter14.blockingQueue;

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class LockTest {
    private static final int SEARCH_THREADS = 100;
    private static final File DUMMY = new File("");
    private static List<File> queue = new ArrayList<>();


    public static void main(String[] args) {
        long startTime = System.currentTimeMillis();
        try (Scanner in = new Scanner(System.in)) {
            System.out.print("Enter base directory (e.g. /opt/jdk1.8.0/src): ");
            String dir = in.nextLine();
            System.out.print("Enter keyword: ");
            String key = in.nextLine();

            try {
                enumerate(new File(dir));
                queue.add(DUMMY);
            }catch (InterruptedException e){

            }

            final int[] count ={0};
            for (int i = 1; i<= SEARCH_THREADS; i++){
                Runnable searcher = () -> {
                    while (true){
                        synchronized (count){
                            boolean done = count[0] == queue.size();
                            if (done){
                                break;
                            }else{
                                try {
                                    search(queue.get(count[0]), key);
                                }catch (IOException e){

                                }
                                count[0]++;
                            }
                        }
                    }
                };
                new Thread(searcher).start();
            }
        }

        long endTime = System.currentTimeMillis();
        System.out.println("耗时："+(endTime-startTime));
    }

    private static void enumerate(File dir) throws InterruptedException {
        File[] files = dir.listFiles();
        for (File file : files){
            if (file.isDirectory()) enumerate(file);
            else queue.add(file);
        }
    }

    private static void search(File file, String key) throws IOException {
        try(Scanner in = new Scanner(file,"UTF-8")){
            int lineNumber = 0 ;
            while (in.hasNextLine()){
                lineNumber++;
                String line = in.nextLine();
                if (line.contains(key)) System.out.printf("%s:%d:%s:%n",file.getPath(),lineNumber,line);
            }
        }
    }
}