error in compilation

[bluesky2319]

I want to add a preprocessing filter and compile the project. But I can't compile the project by default, without any changes. I tried in CentOS 7 and 8, and I get this error:
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:2.3.2:compile (default-compile) on project fdt: Compilation failure
[ERROR] /root/Pictures/fdt-master/src/lia/util/net/common/Config.java:[926,23] error: cannot find symbol
How can I fix this error?
I would appreciate any hints.