Java lambda - for loop counter is not effectively final

Question

Given this situation where a lambda is inside a for loop I would expect the counter i to be effectively final.

The compiler complains that i is not effectively final

Answer 1

You have to remember that a for loop actually equivalent to :

int i=0;
while(i < x.getBooks().size()){
  //execute your block
  i++;
}

So you see that i is declared only once and updated therefore not effectively final.

It's a little unclear the relationship between x.getBooks() and Book.getAuthors() but apparently they have the same size? Without a better understanding, I don't think I can show you a better way to do it. But this might also show you that your design is poor.