I was impressed by your clear writing. Some minor suggestions since you asked for feedback: <:)
* "mandatory requirement" is redundant. If something's not mandatory, then it's not a requirement! :)
* "Many admit that as much as Java is not much fun to write code with, the JVM is a different story.": This sentence is awkward. Perhaps something like: "Many admit Java code is not much fun to write, but the JVM doesn't limit your choice of language."
* "Scala shares the Java Technology Stack, and knowing Java is a big plus when learning Scala, especially due to the common library ecosystem, and the insights into the JVM workings.": This sentence is awkward. It could be simplified into something like: "Knowing Java is a big plus when learning Scala because the languages share a common library ecosystem."
If you are interested in more resources about English writing, I recommend Joseph M. Williams' Style: Toward Clarity and Grace. Strunk & White's Elements of Style is a classic (and short), but some people dislike it.
* "mandatory requirement" is redundant. If something's not mandatory, then it's not a requirement! :)
* "Many admit that as much as Java is not much fun to write code with, the JVM is a different story.": This sentence is awkward. Perhaps something like: "Many admit Java code is not much fun to write, but the JVM doesn't limit your choice of language."
* "Scala shares the Java Technology Stack, and knowing Java is a big plus when learning Scala, especially due to the common library ecosystem, and the insights into the JVM workings.": This sentence is awkward. It could be simplified into something like: "Knowing Java is a big plus when learning Scala because the languages share a common library ecosystem."
If you are interested in more resources about English writing, I recommend Joseph M. Williams' Style: Toward Clarity and Grace. Strunk & White's Elements of Style is a classic (and short), but some people dislike it.