文本文件追加文字

  1. //不加true就是覆盖
  2. try (FileOutputStream fos = new FileOutputStream("data.txt", true)) {
  3.     FileChannel channel = fos.getChannel();
  4.     ByteBuffer src = StandardCharsets.UTF_8.encode("你好你好你好你好你好");
  5.     // 字节缓冲的容量和limit会随着数据长度变化，不是固定不变的
  6.     System.out.println("初始化容量和limit：" + src.capacity() + "," + src.limit());
  7.     int length = 0;
  8.     while ((length = channel.write(src)) != 0) {
  9.         /*
  10.          * 注意，这里不需要clear，将缓冲中的数据写入到通道中后 第二次接着上一次的顺序往下读
  11.          */
  12.         System.out.println("写入长度:" + length);
  13.     }
  14. } catch (IOException e) {
  15.     e.printStackTrace();
  16. }

文件复制

  1. //源文件路径
  2. String from = "data.txt";
  3. //目标文件路径
  4. String to = "to.txt";
  5. try (
  6.         FileChannel fromChannel = new FileInputStream(from).getChannel();
  7.         FileChannel toChannel = new FileOutputStream(to).getChannel()
  8. ) {
  9.     //最多2G
  10.     //fromChannel.transferTo(0,fromChannel.size(),toChannel);
  11.     //超过2G的文件复制写法
  12.     long size = fromChannel.size();
  13.     // left 变量代表还剩余多少字节
  14.     long left = size;
  15.     while (left > 0) {
  16.         left -= fromChannel.transferTo((size - left), left, toChannel);
  17.     }
  18. } catch (IOException e) {
  19.     e.printStackTrace();
  20. }