This is the output of the RussianDoll class, version 4.  

Note that we have to copy the class's source code from RussianDoll4.java to
RussianDoll.java, or the compiler will complain.

$ cp RussianDoll4.java RussianDoll
$ javac RussianDoll.java
$ java RussianDoll
Zero : 0
Zero ++ ++ ++ -- ++ : SSS0
Zero ++ -- -- ++ : S0
Three : SSS0
Four : SSSS0
Three + Four (static method) : SSSSSSS0
Three + Four (instance method) : SSSSSSS0