public void setFileSystemId(String fileSystemId) {
        this.fileSystemId = fileSystemId;
    }
<p>
Specifies which EFS file system to retrieve the <code>FileSystemPolicy</code> for.
</p>

@param fileSystemId
       Specifies which EFS file system to retrieve the <code>FileSystemPolicy</code> for.
aws-java-sdk-efs/src/main/java/com/amazonaws/services/elasticfilesystem/model/DescribeFileSystemPolicyRequest.java