Which of the following are primitive data types? (i) double (ii) String (iii) char (iv) Integer

(i) double and (iii) char are primitive data types.

Java has exactly eight primitives: byte, short, int, long, float, double, char and boolean. Everything else is a reference (non-primitive) type. String is a class, not a primitive — the capital S is the giveaway. Integer is likewise a class, the wrapper for int. The rule of thumb: a type beginning with a capital letter is a class; primitives are always lower case.