java读取文件的几种方式性能比较

    //普通输入流读取文件内容
    public static long checksumInputStream(Path filename)
    {
        try(InputStream in= Files.newInputStream(filename))
        {
            CRC32 crc=new CRC32();
            int c;
            while ((c=in.read())!=-)
            {
                crc.update(c);
            }
            return crc.getValue();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return ;
        }
    }

    //带有缓冲读取文件
    public static long checkSumBufferedInputStream(Path filename)
    {
        try(InputStream in=new BufferedInputStream(Files.newInputStream(filename)))
        {
            CRC32 crc=new CRC32();
            int c;
            while ((c=in.read())!=-)
            {
                crc.update(c);
            }
            return crc.getValue();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return ;
    }

    //随机读取文件
    public static long checksumRandomAccessFile(Path filename)
    {
        try(RandomAccessFile file=new RandomAccessFile(filename.toFile(), "r"))
        {
            long length=file.length();
            CRC32 crc=new CRC32();
            for (int i = ; i < length; i++) {
                file.seek(i);
                int c=file.readByte();
                crc.update(c);
            }
            return crc.getValue();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return ;
    }

    //通过磁盘映射读取文件
    public static long checksumMappedFile(Path filename)
    {
        try(FileChannel channel=FileChannel.open(filename))
        {
            CRC32 crc=new CRC32();
            int length=(int)channel.size();
            MappedByteBuffer buffer= channel.map(FileChannel.MapMode.READ_ONLY, , length);
            for (int i = ; i <length; i++)
            {
                int c=buffer.get(i);
                crc.update(c);
            }
            return crc.getValue();

        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return ;
    }

普通输入流：68513ms

带缓冲的方式：116ms

随机访问读取：81203ms

磁盘映射读取方式：102ms