• 1. 遞歸

package thread;

import java.io.File;

public class Test_basic {

    static String path = "xxxxxxx";

    volatile static int result = 0;
    static final String key = "class";

    public static void main(String[] args) {
        
        long begin = System.currentTimeMillis();
        
        exec(new File(path));
        System.out.println(result);
        System.out.println((System.currentTimeMillis() -begin)+"mm");
        // 2767
        // 806mm
    }

    static void exec(File file) {
        System.out.println(file.getAbsolutePath());
        if (file.isFile()) {
            result += Utils.getCount(file, key);
        } else {
            for (File item : file.listFiles()) {
                exec(item);
            }
        }
    }
}

• 2 線程池

package thread;

import java.io.File;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadPoolExecutor;

public class Test_threadPool {

    static String path = "xxxxxxx";

    volatile static int result = 0;
    static final String key = "class";
    static ThreadPoolExecutor pool = (ThreadPoolExecutor) Executors.newFixedThreadPool(10);

    public static void main(String[] args) {

        long begin = System.currentTimeMillis();

        pool.submit(new ChildThread(path));
        while (pool.getActiveCount() != 0) {
            Thread.yield();
        }
        pool.shutdown();
        
        System.out.println(result);
        System.out.println(System.currentTimeMillis() - begin + "mm");
        // 2767 
        // 562mm
        
    }

    synchronized static void addCount(int num) {
        result = result + num;
    }

    static class ChildThread implements Runnable {

        private String path;

        public ChildThread() {
            super();
        }

        public ChildThread(String path) {
            super();
            this.path = path;
        }

        @Override
        public void run() {
            System.out.println(path);
            File file = new File(path);
            if (file.isFile()) {
                int count = Utils.getCount(file, key);
                addCount(count);
            } else {
                for (File item : file.listFiles()) {
                    pool.submit(new ChildThread(item.getAbsolutePath()));
                }
            }
        }

    }

}

• 3 lambda

package thread;

import java.io.File;
import java.util.stream.Stream;

public class Test_lambda {

    static String path = "xxxxxxx";

    volatile static int result = 0;
    static final String key = "class";

    public static void main(String[] args) {

        long begin = System.currentTimeMillis();

        exec(new File(path));
        System.out.println(result);
        System.out.println((System.currentTimeMillis() - begin) + "mm");
        // 2767
        // 567mm
    }

    static void exec(File file) {
        System.out.println(file.getAbsolutePath());
        if (file.isFile()){
            int count = Utils.getCount(file, key);
            addCount(count);
        } else {
            Stream.of(file.listFiles()).parallel().forEach(i -> {
                exec(i);
            });
        }
    }

    synchronized static void addCount(int num) {
        result = result + num;
    }
}

• 4 forkJoin

package thread;

import java.io.File;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.RecursiveAction;

public class Test_forkJoin {

    static String path = "xxxxxxx";

    volatile static int result = 0;
    static final String key = "class";

    static ForkJoinPool pool = new ForkJoinPool(10);

    public static void main(String[] args) {

        long begin = System.currentTimeMillis();

        exec(new File(path));
        while(pool.getActiveThreadCount()!=0){
            Thread.yield();
        }
        
        System.out.println(result);
        System.out.println((System.currentTimeMillis() - begin) + "mm");
        // 2767
        // 601mm
    }

    static void exec(File file) {
        pool.execute(new MyThread(file, key));
    }

    synchronized static void addCount(int num) {
        result = result + num;
    }

    static class MyThread extends RecursiveAction {

        /**
         * 
         */
        private static final long serialVersionUID = 4794478361974081108L;
        File file;
        String key;

        public MyThread(File file, String key) {
            this.file = file;
            this.key = key;
        }

        @Override
        protected void compute() {
            System.out.println(file.getAbsolutePath());
            if (file.isFile()) {
                int count = Utils.getCount(file, key);
                addCount(count);
            } else {
                for (File item : file.listFiles()) {
                    new MyThread(item, key).fork();
                }
            }
        }

    }
}