Hold on, but what if you want your Java to be fast, you could rewrite it into...
Hold on, but what if you want your Java to be fast, you could rewrite it into COBOL. Then as soon as the rewite is done, modernize by translating into Java, then back to COBOL for performance, but don't stop there..
Self-replies
I think COBOL should be rewritten to go or rust. A rewrite into a slow language is going to mess with one of the reasons it is still cobol.