What is the solution and how???

Question

int y=8 ;
y+= ++y + y-- + --y ?

In blueJ (Java)

But the answer is 33

Answer 1

There is no solution because this is undefined behaviour.
For c++ the output is:
gcc and vc++ y = 31
clang y = 32

For java there probably won't be much difference.

Don't use more than 1 increment/decrement operator in 1 expression, it's also very ugly and unreadable.