Why can't int have a null value, but Integer has a null value?

The int type variable is the primitive type variable. For this reason, we go to the real value storage place, but the Integertype variable is reference type, which is the address of the object, not the actual value That's why you can have a null.

What is the difference between int vs Integer?

int (Primitive data type (long, float, double, . . .)

Integer (Wrapper class (object)