What's the best way to help Lemmy users organise into productive communities?

On Reddit we have:

• r/java - Java news and discussion. Not about learning the language or getting help with Java problems
• r/learnjava - learning to use the Java language, platform, its tools, or parts of its ecosystem (libraries)
• r/javahelp - Getting help with Java (in practice, much the same content as r/learnjava)

So far, on Lemmy I've found the following (with only the very start of an active membership building up in each)

• Java™ Community@lemmy.ml - One option for replacing r/java
• java@programming.dev - Another candidate for replacing r/java
• Learn Java@lemmy.world - a possible replacement for r/learnjava and r/javahelp

Are there other communities out there already?

How do we avoid fragmentation? Where there's overlap, are there reasoned opinions on how to converge (eg matching instance policies to the audience)?

Do we just encourage communities to peer-link until critical mass develops and community activity-levels speak for themselves? Or is that just likely to split the community until community owners promote migration towards a 'common space' for each type of content?