Java-Io-RandomAccessFile任意位置读写数据的操作小结

try (
         RandomAccessFile r = new RandomAccessFile(new File(readFile), "r");
         RandomAccessFile w = new RandomAccessFile(new File(writeFile), "rw");
        ){
      w.seek(w.length()); // 将指针指向文件最后,进行追加
      byte[] bytes = new byte[1024];
      int len = -1;
      while ((len = r.read(bytes)) != -1) {
        w.write(bytes);
      }
    } catch (IOException e) {
      e.printStackTrace();
    }

 CodeStartAndStopTimeUtil.creator(
        () -> {
          File file = ResourceFileUtil.getFile("mp4/mp4_2.zip");
          String readFile = file.getAbsolutePath();
          String writeFile = file.getParent() + File.separator + "mp4_11112.zip";
          byte[] bytes = new byte[2048];
          try (RandomAccessFile r = new RandomAccessFile(new File(readFile), "r");
              RandomAccessFile w = new RandomAccessFile(new File(writeFile), "rw"); ) {
            int len = -1;
            while ((len = r.read(bytes)) != -1) {
              w.write(bytes);
            }
          }
        });
  }

CodeStartAndStopTimeUtil.creator(
        () -> {
          File file = ResourceFileUtil.getFile("mp4/mp4.zip");
          String readFile = file.getAbsolutePath();
          String writeFile = file.getParent() + File.separator + "mp4_11112.zip";
          long length = new File(readFile).length(); // 文件一共大小
          int num = (int)length/8; // 每个线程读写多少字节   20971520(20mb)  2.5个g4~5秒左右
          List<long[]> longs = DataGroup.dataGroupOnce(length, num);
          List<Future<?>> futures = new ArrayList<>();
          for (long[] aLong : longs) {
            long l = aLong[0]; // 起始位置
            // 创建线程并运行
            Future<?> randomAccessFile =
                ExecutorUtils.createFuture(
                    "RandomAccessFile",
                    () -> {
                      byte[] bytes = new byte[num];
                      try (
                      // 在线程内部创RandomAccessFile对象
                      RandomAccessFile r = new RandomAccessFile(new File(readFile), "r");
                      RandomAccessFile w = new RandomAccessFile(new File(writeFile), "rw"); ) {
                        r.seek(l);
                        int len = r.read(bytes);
                        if (len < num) {
                          // 调整数组
                          bytes = ArrayByteUtil.getActualBytes(bytes);
                        }
                        // 写入文件
                        w.seek(l);
                        w.write(bytes);
                        System.out.println(l );
                      } catch (IOException e) {
                        e.printStackTrace();
                      }
                    });
            futures.add(randomAccessFile);
          }
          // 阻塞全部线程执行完毕
          ExecutorUtils.waitComplete(futures);
        });

//需要重新转码才能正常显示
   System.out.println( 
   new String(r.readLine().getBytes(StandardCharsets.ISO_8859_1), StandardCharsets.UTF_8)
   );