title: If it's "Write once run anywhere", why do so many Java programs tell me to pick the version for my OS?
body: <p>I am fairly new to Java or programming in general. On my journeys through the internet to master this language I have come up the saying "write once run anywhere" multiple times.</p>
  
  <p>But I have found many software that requires you to pick the right version for your OS. Sometimes there is only one version available.</p>
  
  <p>Could you explain to me why that is so?</p>