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Java has two "categories" of types: primitive types and reference types.

Primitive Types
Primitive data types are generally used for local variables, parameters and instance variables (properties of an object). Primitive data types are located on the stack and we can only access their value, while objects are located on heap and we have a reference to those objects. Also, when invoking methods in java, primitive data types are always passed by value and objects are always passed by reference. All the primitive types have specified sizes that are machine independent for portability.

boolean	same as bool in C++ 1 byte in size
char	holds one 16 bit unicode character 2 bytes in size
byte	8-bit signed integer 1 byte in size
short	16-bit signed integer 2 bytes in size
int	32-bit signed integer 4 bytes in size
long	64-bit signed integer 8 bytes in size
float	floating-point number 4 bytes in size
double	double precision floating-point number 8 bytes in size

Reference Types
Arrays and objects of classes are the examples of Java reference types. Arrays and classes are discussed in the coming lessons. There are no struct, union, enum, unsigned, typedef, or pointer types in Java.

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