to write properties file (Java) normally I use this in linux (mint and ubuntu distributions):
$ native2ascii filename.properties
For example:
$ cat test.properties
first=Execução número um
second=Execução número dois
$ native2ascii test.properties
first=Execu\u00e7\u00e3o n\u00famero um
second=Execu\u00e7\u00e3o n\u00famero dois
PS: I writed Execution number one/two in portugues to force special characters.
In my case, in first execution I received this message:
$ native2ascii teste.txt
The program 'native2ascii' can be found in the following packages:
* gcj-5-jdk
* openjdk-8-jdk-headless
* gcj-4.8-jdk
* gcj-4.9-jdk
Try: sudo apt install <selected package>
When I installed the first option (gcj-5-jdk) the problem was finished.
I hope this help someone.