Probably Java, much as it pains me to say that. Mature language and ecosystem, will have longevity for decades more since it's as deeply embedded in business systems as COBOL was, and can be used for cross-platform GUI applications with a bit of effort.
(Python may be easier but, thanks to the GIL, doesn't deal well with multiple threads of execution and that's the name of the game to get performance from modern multi-core systems.)
Probably Java, much as it pains me to say that. Mature language and ecosystem, will have longevity for decades more since it's as deeply embedded in business systems as COBOL was, and can be used for cross-platform GUI applications with a bit of effort.
(Python may be easier but, thanks to the GIL, doesn't deal well with multiple threads of execution and that's the name of the game to get performance from modern multi-core systems.)