Expression Editor: how to add own Functions

[luke2000]

I am using Jaspersoft Studio 6.6 and try to add own functions to the Expression Editor.

Therefore i follow the tutorial here Jaspersoft Studio Expression Editor: how to extend it and contribute your own functions (part 2) - updated for version 5.5

All works fine but i had to replace the language of the generated report (SampleFunctionsReport.jrxml) from groovy to java to get rid of file not found exceptions

Finally after fixing this i still have the following Errors

Description    Resource    Path    Location    Type
The method HELLO_WORLD_MSG() is undefined for the type SampleFunctions_1541665022158_603382    SampleFunctionsReport.jrxml    /MyFunctions    line 37    JRXML Problem
The method HELLO_WORLD_MSG() is undefined for the type SampleFunctions_1541665022158_603382 value = HELLO_WORLD_MSG( );     SampleFunctionsReport.jrxml    /MyFunctions    line 0    JRXML Problem
The method REPEAT_MSG(String, int, boolean) is undefined for the type SampleFunctions_1541665022158_603382    SampleFunctionsReport.jrxml    /MyFunctions    line 52    JRXML Problem
The method REPEAT_MSG(String, int, boolean) is undefined for the type SampleFunctions_1541665022158_603382 value = REPEAT_MSG("A message that will be probably repeated",5,true);     SampleFunctionsReport.jrxml    /MyFunctions    line 0    JRXML Problem

I checked the tutorial a couple of times...
What am i missing?