文件拷贝， 使用 BIO,NIO的对比，四种写法性能分析。

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package test;

import java.io.BufferedInputStream;

import java.io.BufferedOutputStream;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.nio.MappedByteBuffer;

import java.nio.channels.FileChannel;

public class FileCopyTest

{

    public FileCopyTest()

    {

        File[] files = new File("c:/images").listFiles();

        String destFolderPath = "g:/images";

        long t = System.currentTimeMillis();

        try

        {

            for (File sourceFile : files)

            {

                traditionalCopy(sourceFile.getPath(), destFolderPath + "/" + sourceFile.getName());

            }

        }

        catch (Exception e)

        {

            e.printStackTrace();

        }

        System.out.println("传统IO方法实现文件拷贝耗时:" + (System.currentTimeMillis() - t) + "ms");

        //删除刚刚创建的

        for (File file : new File(destFolderPath).listFiles())

        {

            file.delete();

        }

        t = System.currentTimeMillis();

        try

        {

            for (File sourceFile : files)

            {

                copyBIO(sourceFile.getPath(), destFolderPath + "/" + sourceFile.getName());

            }

        }

        catch (Exception e)

        {

            e.printStackTrace();

        }

        System.out.println("传统IO + 缓存 方法实现文件拷贝耗时:" + (System.currentTimeMillis() - t) + "ms");

        //删除刚刚创建的

        for (File file : new File(destFolderPath).listFiles())

        {

            file.delete();

        }

        t = System.currentTimeMillis();

        try

        {

            for (File sourceFile : files)

            {

                nioCopy(sourceFile.getPath(), destFolderPath + "/" + sourceFile.getName());

            }

        }

        catch (Exception e)

        {

            e.printStackTrace();

        }

        System.out.println("利用NIO文件通道方法实现文件拷贝耗时:" + (System.currentTimeMillis() - t) + "ms");

        //删除刚刚创建的

        for (File file : new File(destFolderPath).listFiles())

        {

            file.delete();

        }

        t = System.currentTimeMillis();

        try

        {

            for (File sourceFile : files)

            {

                nioCopy2(sourceFile.getPath(), destFolderPath + "/" + sourceFile.getName());

            }

        }

        catch (Exception e)

        {

            e.printStackTrace();

        }

        System.out.println("利用NIO文件内存映射及文件通道实现文件拷贝耗时:" + (System.currentTimeMillis() - t) + "ms");

        //删除刚刚创建的

        for (File file : new File(destFolderPath).listFiles())

        {

            file.delete();

        }

    }

    private static void traditionalCopy(String sourcePath, String destPath) throws Exception

    {

        File source = new File(sourcePath);

        File dest = new File(destPath);

        FileInputStream fis = new FileInputStream(source);

        FileOutputStream fos = new FileOutputStream(dest);

        byte[] buf = new byte[8192];

        int len = 0;

        while ((len = fis.read(buf)) != -1)

        {

            fos.write(buf, 0, len);

        }

        fis.close();

        fos.close();

    }

    private static void copyBIO(String sourcePath, String destPath) throws Exception

    {

        File source = new File(sourcePath);

        File dest = new File(destPath);

        BufferedInputStream bis = new BufferedInputStream(new FileInputStream(source));

        BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(dest));

        byte[] buf = new byte[8192];

        int len = 0;

        while ((len = bis.read(buf)) != -1)

        {

            bos.write(buf, 0, len);

        }

        bis.close();

        bos.close();

    }

    private static void nioCopy(String sourcePath, String destPath) throws Exception

    {

        File source = new File(sourcePath);

        File dest = new File(destPath);

        FileInputStream fis = new FileInputStream(source);

        FileOutputStream fos = new FileOutputStream(dest);

        FileChannel sourceCh = fis.getChannel();

        FileChannel destCh = fos.getChannel();

        destCh.transferFrom(sourceCh, 0, sourceCh.size());

        sourceCh.close();

        destCh.close();

    }

    private static void nioCopy2(String sourcePath, String destPath) throws Exception

    {

        File source = new File(sourcePath);

        File dest = new File(destPath);

        FileInputStream fis = new FileInputStream(source);

        FileOutputStream fos = new FileOutputStream(dest);

        FileChannel sourceCh = fis.getChannel();

        FileChannel destCh = fos.getChannel();

        MappedByteBuffer mbb = sourceCh.map(FileChannel.MapMode.READ_ONLY, 0, sourceCh.size());

        destCh.write(mbb);

        sourceCh.close();

        destCh.close();

    }

}