Can you elaborate a bit more about where you are running your Java application? For example, in this Cloud Run guide, the NFS from the Filestore instance is mounted to the Cloud Run container, at which point you can access the File System from Java code. All the code from this guide is hosted in this repository. It includes methods to write and read files in the mounted file system. If you have issues in how to mount the file system in various environments, you can check this documentation page.