import java.io.File;
import java.io.IOException;
import java.nio.file.FileVisitResult;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.SimpleFileVisitor;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.Set;

public class FIter {
    
    public static void main(String[] args) throws IOException {

        System.out.println("java.io.File iteration");
        Info info = null;
        long t = 0;

        // fs warmup
        ioIter(new File[] { new File(args[0])}, new Info());

        for (int i = 0; i < 10; i++) {
            info = new Info();    
            long t0 = System.currentTimeMillis();
            ioIter(new File[] { new File(args[0])}, info);
            long t1 = System.currentTimeMillis();
            t += (t1 - t0);
        }
        System.out.println("------------------");        
        System.out.println("  io.totalSize:" + info.size);
        System.out.println("        fileNum:" + info.num);
        System.out.println("       checkSum:" + info.csum);
        System.out.println("          Time:" + t/10);


        ioIter2(null, new String[] { args[0]}, new Info());

        for (int i = 0; i < 10; i++) {
            info = new Info();    
            long t0 = System.currentTimeMillis();
            ioIter2(null, new String[] { args[0]}, info);
            long t1 = System.currentTimeMillis();
            t += (t1 - t0);
        }
        System.out.println("------------------");        
        System.out.println(" io2.totalSize:" + info.size);
        System.out.println("        fileNum:" + info.num);
        System.out.println("       checkSum:" + info.csum);
        System.out.println("          Time:" + t/10);


        nioIter(args[0], new Info());
        t = 0;
        for (int i = 0; i < 10; i++) {
            info = new Info();    
            long t0 = System.currentTimeMillis();
            nioIter(args[0], info);
            long t1 = System.currentTimeMillis();
            t += (t1 - t0);
        }
        System.out.println("------------------");        
        System.out.println("  nio.totalSize:" + info.size);
        System.out.println("        fileNum:" + info.num);
        System.out.println("       checkSum:" + info.csum);
        System.out.println("           Time:" + t/10);

        
    }
    
    static class Info {
        long size;
        int  num;
        long csum;
    }
    
    private static void ioIter(File[] files, Info info) {
        if (files == null)
            return;
        
        for (File f : files) {
            info.num++;            
            info.csum += f.lastModified();            
            if (f.isFile()) {
                info.size += f.length();

            } else if (f.isDirectory()) {
                ioIter(f.listFiles(), info);

            } else {}  // just ignore
         }
    }

    private static void ioIter2(File dir, String[] files, Info info) {
        if (files == null)
            return;
        
        for (String fn : files) {
            File f;
            if (dir == null) {
                f = new File(fn);
            } else {
                f = new File(dir, fn);
            }
            info.num++;            
            info.csum += f.lastModified();            
            if (f.isFile()) {
                info.size += f.length();

            } else if (f.isDirectory()) {
                ioIter2(f, f.list(), info);

            } else {}  // just ignore
         }
    }

    
    private static void nioIter(String dir, final Info info) throws IOException {
        Path path = Paths.get(dir);
        Files.walkFileTree(
            path,
            new SimpleFileVisitor<Path>() {
                @Override
                public FileVisitResult visitFile(Path file,
                                                 BasicFileAttributes attrs)
                {
                    info.size += attrs.size();
                    info.csum += attrs.lastModifiedTime().toMillis();
                    info.num++;
                    return FileVisitResult.CONTINUE;
                }

                @Override
                public FileVisitResult preVisitDirectory(Path dir,
                                                         BasicFileAttributes attrs)
                {
                     info.num++;
                     info.csum += attrs.lastModifiedTime().toMillis();                     
                     return FileVisitResult.CONTINUE;
                }
        });        
    }
}