Why does Java require an explicit cast on a final variable if it was copied from an array?

Question

Starting with the following code...

byte foo = 1;
byte fooFoo = foo + foo;

When I try compiling this code I will get the following error...

Answer 1

This occurs because of

byte foo = 1;
byte fooFoo = foo + foo;

foo + foo = 2 will be answered but 2 is not byte type because of java has default data type to integer variables it's type is int. So you need to tell the compiler by force that answer must be a byte type explicitly.

class Example{
    public static void main(String args[]){

        byte b1 = 10;
        byte b2 = 20;
        byte b1b2 = (byte)(b1 + b2); 

        //~ b1 += 100;  // (+=) operator automaticaly type casting that means narrow conversion

        int tot = b1 + b2;

        //~ this bellow statement prints the type of the variable
        System.out.println(((Object)(b1 + b2)).getClass());  //this solve your problem
    }
}