The code sample you have provided is not valid in java. The private access modifier can be applied to members and methods, including inner classes. Your code compiles in Eclipse, but is rejected by Oracle's own compiler.
In fact, the byte-code generated by Eclipse for this java code, is exactly the same with or without that private keyword. This shows that this is probably an Eclipse bug where it ignores the text before the word package during compilation.
What you have probably read or heard, is the phrase "package-private", which means that nothing outside the package can access the class or member. You do this by not using any access modifier on the class itself. Not by using the private keyword on the package.
