MappedByteBuffer

内存映射文件：操作内存，内存帮我们写入到磁盘

/** * A direct byte buffer whose content is a memory-mapped region of a file. * * <p> Mapped byte buffers are created via the {@link * java.nio.channels.FileChannel#map FileChannel.map} method. This class * extends the {@link ByteBuffer} class with operations that are specific to * memory-mapped file regions. * * <p> A mapped byte buffer and the file mapping that it represents remain * valid until the buff