I dont Know what you mean!
having primitive type is for simplicity and Campatibilty with C and
C++;
you can cast your primitive to object form ver easy to have a better
Control on those data type and having lots of related methods.
how ever in jdk 1.5 you you hava never need casting.
type casting is automatic and the statements like

int i1 = 5;
Integer i2 = new Integer();
i2 = i1;

are absolutly legal whit no error.

Something that no others programming language have and I know they
wont have this facility soon.