...Uses or Overrides Deprecated API...

Got this error message in a gradle error log.  How to fix?

C:\Pylo\MCreator179\forge\build\sources\main\java\mod\mcreator\mcreator_bloodAltarGUI.java:77: error: cannot find symbol
            if (ent != null && (ent instanceof mcreator_bloodAltar.TileEntityCustom))
                                                                  ^
  symbol:   class TileEntityCustom
  location: class mcreator_bloodAltar
Note: Some input files use or override a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
1 error

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':compileJava'.
> Compilation failed; see the compiler error output for details.

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.