You would be surprised - or rather shocked - how many enterprises still run on it.
I doubt we'll get around to the Java 8 stuff before 2030.
99% of the work was redesigning the business process it supports to be in compliance, and then write a new LOB app that takes inspiration from the old one, but works with the new process.
You might be able to use AI for the remaining 1% mind- and pointless boilerplate code Java requires for no good reason.