public void unmmap() {
        if (isMapped()) {
            this.mapLock.lock();
            try {
                if (isMapped()) {
                    this.mappedByteBuffer.force();
                    this.flushedPosition.set(getWrotePosition());
                    if (this.mappedByteBuffer != null) {
                        if (Platform.isLinux()) {
                            hintUnload();
                        }
                        Utils.unmap(this.mappedByteBuffer);
                    }
                    this.isMapped = false;
                }
            } catch (final Throwable t) {
                LOG.error("error unmap file {} , {}", getFilePath(), t);
                throw new RuntimeException(t);
            } finally {
                this.mapLock.unlock();
            }
        }
    }
File parent class that wrappers uniform functions such as mmap(), flush() etc..
@author hzh (642256541@qq.com)
jraft-extension/java-log-storage-impl/src/main/java/com/alipay/sofa/jraft/storage/file/AbstractFile.java