What are the keywords which is used internally by java but programmer can't use it?

Actually keywords means words which are used internally in Java and hence cannot be used by the programmer. as they are used for special purposes by Java language.

There are50 keywords which cannot be used by programmers, initially they are47 but then some additions has been made in later versions of Jdk and may continue in future also.

I am not aware of any such keywords that is internally used by Java but programmer can't user it.

However, there are two keywords, const and goto reserved by Java, even though they are not currently used.