类型转换：byte vs int (Java)

Question

    byte b = 1;
    b = -b; //i get highlited in red in here
    
    int a = 1;
    a = -a; //it is ok for jvm

why if (b = -b), then I get a mistake, but if i do the same with int, it is OK? What is the reason?

Sorry for such a newbie question, but I can't understand reason myself, neither found answer in google of SO.

Answer 1

There is a good article " The mystery of the negative byte value in Java ".

Also,

Red highlighted tell you:

Required type: byte

Provided: int

So, unary minus operator cast byte to int .