title: rt.jar com.sun.istack.internal packages
body: <p>jre comes with many libraries in rt.jar one of which is com.sun.istack.internal*. I needed the documentation of com.sun.istack.internal.Nullable(<strike>which I found being used by google in its CacheBuilder</strike>) and first I thought was to go to docs.oracle.com to find its documentation and there I found nothing about it. Next went to source folder sourced with jdk and I didn't find com name entity in the said folder. Next I take a look at the jre7 release and take a look at all the packages and class and found no mention of Nullable there. Though SO had one <a href="https://stackoverflow.com/questions/4963300/which-notnull-java-annotation-should-i-use">mention of it</a>, but nothing concrete. I am still puzzled where to get its documentaion and src if needed. I even looked legacy sun api documentation at oracle but nothing mentioned about it. where does oracle document there policy about ported packages and their being standard or not-standard.They must have documented it somewhere it is just that I'm taking too much of time to get there. </p>
  
  <p>Please point me there.</p>
  
  <p>EDIT: Actually the javax.annotation.Nullable is being used in google CacheBuilder and not com.sun.istack.internal.Nullable.
  Also for someone who may face this issue: javax.annotation.Nullable is not part of Java SE as of now, and it is being ported in jsr305 jar. So if you are planning to use CacheBuilder or just going through its code, do add jsr305 jar in your class path, else eclipse get confuse and will point you to com.sun.istack.intenal.Nullable when ever you hover your cursor over Nullable.</p>