in detail:
if we use public API for example, write java program for example , in JDK 1.4, if should run correctly in all version above it. in all update version in 1.4, in 1.5, 1.6 and 1.7?
Also , what is the combability rule between different updater versions , for example 1.6.22 and 1.6.23 what can not be changed, what can be changed?
of course, public API definition can not be changed, how about others? javadoc? internal API definition, implementation?
It will be great if someone can point a concrete official document on this topic. thanks,
there is one example in java document bug, that they intended not to change between updater version. see https://bugs.java.com/bugdatabase/view_bug?bug_id=6475885
this should be one of its big picture, but we better to have a complete description on this.
need to know the complete story so that we feel safe to upgrade to bigger version.
This is not a full answer but I will add that will-it-run and will-it-compile are two different things. Keywords introduced in 1.5 will prevent some 1.4 code from compiling but the byte code will run just fine.