java 获取文件长度的几种方法的效率比较

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刚才使用如下代码进行测试，得到了如下下的结果！！

import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.IOException;import java.io.RandomAccessFile;import java.nio.channels.FileChannel;import java.nio.file.Path;import java.nio.file.Paths;/** * Created by yangjunlin on 8/14/15. */public class FileTest{    public static void main(String[] dd)    {        Path path = Paths.get("/home/yangjunlin/Downloads/ubuntu-14.04.2-desktop-amd64.iso");        System.out.println(path.getFileName());        long begin1 = System.nanoTime();        try (RandomAccessFile randomAccessFile = new RandomAccessFile(path.toFile(), "rw"))        {            System.out.println("RandomAccessFile length: " + randomAccessFile.length());            System.out.println("RandomAccessFile nanoTime: " + (System.nanoTime() - begin1));        }        catch (FileNotFoundException e)        {            e.printStackTrace();        }        catch (IOException e)        {            e.printStackTrace();        }        long begin2 = System.nanoTime();        System.out.println("File length: " + path.toFile().length());        System.out.println("File nanoTime: " + (System.nanoTime() - begin2));        long begin3 = System.nanoTime();        try (FileInputStream fileInputStream = new FileInputStream(path.toFile()))        {            System.out.println("FileInputStream length: " + fileInputStream.available());            System.out.println("FileInputStream nanoTime: " + (System.nanoTime() - begin3));        }        catch (FileNotFoundException e)        {            e.printStackTrace();        }        catch (IOException e)        {            e.printStackTrace();        }        long begin4 = System.nanoTime();        try (FileChannel fileChannel = new FileInputStream(path.toFile()).getChannel())        {            System.out.println("FileChannel length: " + fileChannel.size());            System.out.println("FileChannel nanoTime: " + (System.nanoTime() - begin4));        }        catch (FileNotFoundException e)        {            e.printStackTrace();        }        catch (IOException e)        {            e.printStackTrace();        }    }}

结果如下：

ubuntu-14.04.2-desktop-amd64.iso
RandomAccessFile length: 1044381696
RandomAccessFile nanoTime: 449054
File length: 1044381696
File nanoTime: 80385
FileInputStream length: 1044381696
FileInputStream nanoTime: 108946
FileChannel length: 1044381696
FileChannel nanoTime: 3220354

装饰越多越慢呀。

在读超大文件的时候会有坑，见这里：http://blog.csdn.net/chaijunkun/article/details/22387305

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