3.2 两个 Channel 传输数据

String FROM = "helloword/data.txt"; String TO = "helloword/to.txt"; long start = System.nanoTime(); try (FileChannel from = new FileInputStream(FROM).getChannel(); FileChannel to = new FileOutputStream(TO).getChannel(); ) { from.transferTo(0, from.size(), to); } catch (IOException e) { e.printStackTrace(); } long end = System.nanoTime(); System.out.println("transferTo 用时：" + (end - start) / 1000_000.0);

超过 2g 大小的文件传输

public class TestFileChannelTransferTo { public static void main(String[] args) { try ( FileChannel from = new FileInputStream("data.txt").getChannel(); FileChannel to = new FileOutputStream("to.txt").getChannel(); ) { // 效率高，底层会利用操作系统的零拷贝进行优化 long size = from.size(); // left 变量代表还剩余多少字节 for (long left = size; left > 0; ) { System.out.println("position:" + (size - left) + " left:" + left); left -= from.transferTo((size - left), left, to); } } catch (IOException e) { e.printStackTrace(); } } }