What's the aim of not used java keyword?

Question

As oracle states, const is a keyword in java. But it is not used. So why is it so and what's the use of const being a non used keyword in java? (the same goes for goto)

Answer 1

From the Java Language Specification:

The keywords const and goto are reserved, even though they are not currently used. This may allow a Java compiler to produce better error messages if these C++ keywords incorrectly appear in programs.

(This wording already was in the first edition, I think.)