MappedByteBuffer对文件进行读写使用示例

import cn.hutool.core.lang.Assert;

import java.io.IOException;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;

import static java.nio.channels.FileChannel.MapMode.READ_ONLY;
import static java.nio.channels.FileChannel.MapMode.READ_WRITE;

/**
 * ClassName: aaaaa
 * Description:
 * @author king
 */
public class aaaaa {
    private final static String CONTENT = "Zero copy implemented by MappedByteBuffer";
    private final static String FILE_NAME = "mmap.txt";
    private final static String CHARSET = "UTF-8";

    public static void main(String[] args) {
        dushuju();
    }
  public static void xieshuju(){
      /**写文件数据
       * 打开文件通道 fileChannel 并提供读权限、写权限和数据清空权限，通过 fileChannel 映射到一个可写的内存缓冲区 mappedByteBuffer，
       * 将目标数据写入 mappedByteBuffer，通过 force() 方法把缓冲区更改的内容强制写入本地文件。
       */
      Path path = Paths.get("E:\\data",FILE_NAME);
      byte[] bytes = CONTENT.getBytes(Charset.forName(CHARSET));
      try (FileChannel fileChannel = FileChannel.open(path, StandardOpenOption.READ,
              StandardOpenOption.WRITE, StandardOpenOption.TRUNCATE_EXISTING)) {
          MappedByteBuffer mappedByteBuffer = fileChannel.map(READ_WRITE, 0, bytes.length);
          if (mappedByteBuffer != null) {
              mappedByteBuffer.put(bytes);
              mappedByteBuffer.force();
          }
      } catch (IOException e) {
          e.printStackTrace();
      }
  }
    public static void dushuju(){
        /**
         * 读文件数据：打开文件通道 fileChannel 并提供只读权限，通过 fileChannel 映射到一个只可读的内存缓冲区 mappedByteBuffer，
         * 读取 mappedByteBuffer 中的字节数组即可得到文件数据。
         * */
        Path path = Paths.get("E:\\data",FILE_NAME);
        int length = CONTENT.getBytes(Charset.forName(CHARSET)).length;
        try (FileChannel fileChannel = FileChannel.open(path, StandardOpenOption.READ)) {
            MappedByteBuffer mappedByteBuffer = fileChannel.map(READ_ONLY, 0, length);
            if (mappedByteBuffer != null) {
                byte[] bytes = new byte[length];
                mappedByteBuffer.get(bytes);
                String content = new String(bytes, StandardCharsets.UTF_8);
                System.out.println(content);
                Assert.equals(content, "Zero copy implemented by MappedByteBuffer");
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}