java 快速读取文件的方法。

[the_chose_one]

我用了Imageio.read(new File(路径)); 但是读取图片感觉还是不够快，1M的图片需要400毫米才读取完。请大神指点。

[郑涛]

/** * 内存映射 * * @throws IOException */ public static void mapChannel() throws IOException { long t1 = System.currentTimeMillis(); FileInputStream in = new FileInputStream("d:/1.txt"); long size = in.available(); RandomAccessFile out = new RandomAccessFile("d:/2.txt", "rw"); FileChannel inc = in.getChannel(); MappedByteBuffer bf = inc.map(FileChannel.MapMode.READ_ONLY, 0, size); FileChannel outc = out.getChannel(); MappedByteBuffer outbf = outc.map(FileChannel.MapMode.READ_WRITE, 0, size); outbf.put(bf); inc.close(); outc.close(); in.close(); out.close(); long t2 = System.currentTimeMillis(); System.out.println(t2 - t1); } (完全的内存映射)读文件是最快的,比任何其它读取方式快40倍,但你要BufferedImage结果那只能读到内存了

[the_chose_one]

谢谢，那我试试啊！

[sca4441479]

1L+1，NIO确实

[Inhibitory]

Imageio.read(new File(路径)); 不只是读取文件，还要解析图像。

[jdgdf566]

引用 1 楼 qq331077064 的回复:

/** * 内存映射 * * @throws IOException */ public static void mapChannel() throws IOException { long t1 = System.currentTimeMillis(); FileInputStream in = new FileInputStream("d:/1.txt"); long size = in.available(); RandomAccessFile out = new RandomAccessFile("d:/2.txt", "rw"); FileChannel inc = in.getChannel(); MappedByteBuffer bf = inc.map(FileChannel.MapMode.READ_ONLY, 0, size); FileChannel outc = out.getChannel(); MappedByteBuffer outbf = outc.map(FileChannel.MapMode.READ_WRITE, 0, size); outbf.put(bf); inc.close(); outc.close(); in.close(); out.close(); long t2 = System.currentTimeMillis(); System.out.println(t2 - t1); } (完全的内存映射)读文件是最快的,比任何其它读取方式快40倍,但你要BufferedImage结果那只能读到内存了

你试试比较一下使用BufferedInputStream(InputStream in, int size)，把缓冲设置的大一点。与nio比较一下，给大家个回复。

[jdgdf566]

楼主看看这个帖子：http://www.iteye.com/topic/866622

[jdgdf566]

引用 1 楼 qq331077064 的回复:

/** * 内存映射 * * @throws IOException */ public static void mapChannel() throws IOException { long t1 = System.currentTimeMillis(); FileInputStream in = new FileInputStream("d:/1.txt"); long size = in.available(); RandomAccessFile out = new RandomAccessFile("d:/2.txt", "rw"); FileChannel inc = in.getChannel(); MappedByteBuffer bf = inc.map(FileChannel.MapMode.READ_ONLY, 0, size); FileChannel outc = out.getChannel(); MappedByteBuffer outbf = outc.map(FileChannel.MapMode.READ_WRITE, 0, size); outbf.put(bf); inc.close(); outc.close(); in.close(); out.close(); long t2 = System.currentTimeMillis(); System.out.println(t2 - t1); } (完全的内存映射)读文件是最快的,比任何其它读取方式快40倍,但你要BufferedImage结果那只能读到内存了

你试试比较一下使用BufferedInputStream(InputStream in, int size)，把缓冲设置为1024 * 32（我的机器，你的机器可能更大一点）。与nio比较一下，给大家个回复。