Java has two categories of data types: Primitive Data Types: Java has eight primitive data types which are used to represent basic values like numbers, characters, and boolean values. They are: byte: 8-bit signed integer value. short: 16-bit signed integer value. int: 32-bit signed integer value. long: 64-bit signed integer value. float: 32-bit floating point value. double: 64-bit floating point value. char: 16-bit Unicode character value. boolean: represents true/false values. Reference Data Types: Reference data types are used to refer to objects. They are: Class: represents a class or interface. Array: represents an array. Interface: represents an interface. String: represents a sequence of characters. Enumeration: represents an enumeration type. Wrapper classes: provides a way to use primitive data types as objects. Annotation: represents an annotation type. Note that, all of the primitive data types in Java have a corresponding wrapper class in the java.lang package. These wrapper classes are used to convert primitive data types to objects and vice versa.