id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
23564	Java 21 migration	taylor.smock	team	"Followup of #17858

Timelines:
* 2023-10-03: Build installer packages with Java 21 => r18848
* 2023-12-21: OpenWebStart supports Java 21
* 2024-03-20: Update Debian/Ubuntu launch script to prefer 21 over 17 and 11 => r19018
* ????-??-??: Debian switches to Java 21 ([https://packages.debian.org/experimental/default-jre experimental] is on Java 21 as of 2024-03-20)
* ????-??-??: Ubuntu LTS switches to Java 21
* ????-??-??: Enough users have switched to Java 21 that we can move codebase to Java 21 after transition phase
* ????-??-??: Start warning users that their version of Java will be unsupported during startup (1 month), then stop allowing JOSM to finish startup (1-3 months), then start compiling JOSM with Java 21 features."	task	new	normal	Longterm	Core			java21	stoecker sebastic