Primitive vs. Reference Data Types
Primitives vs. References
- primitive types are the basic types of data
byte, short, int, long, float, double, boolean, char- primitive variables store primitive values
- reference types are any instantiable class as well as arrays
String, Scanner, Random, Die, int[], String[], etc.- reference variables store addresses
Assignment
- copies the contents of RHS variable into LHS variable
- primitives: the primitive value is copied
- references: the address is copied
- implications: for references the object is not copied, it is
shared (reference variables are aliases)
Comparisons (e.g. ==)
- compares the contents of the variables
- primitives: the primitive values are compared
- references: the addresses are compared
- implications: for references the contents of the objects are
not compared
Passing Parameters
- terminology:
- formal parameter: the parameter variable that is listed (along with its
type) in the method declaration
- actual parameter: the parameter that is given when the method is called
- copies the contents of actual parameter into the formal parameter (i.e.,
pass-by-value)
- primitives: the primitive value is copied
- references: the address is copied
- implications: for references the object is not copied, it is
shared (i.e., actual parameter and formal parameter are aliases)
- primitives: changing the formal parameter's value doesn't affect the
actual parameter's value
- references: changing the formal parameter's address doesn't affect the
actual parameter's address but changing the formal parameter's object does change
the actual parameter's object since they refer to the same object
Returning Values
- returns a result to where the method was called
- primitives: the primitive value is returned
- references: the address is returned
- recall: local variables and parameters are destroyed when the
method finishes execution
- implications: a locally created object can survive if it is
returned or if it is stored in a data member