Final answer:
To identify public instance variables, examine the class code for variables declared without 'private' or 'protected', or explicitly as 'public'. Count those that are accessible from outside the class.
Step-by-step explanation:
To determine how many public instance variables a class has, you would need to look at the class definition in the code. Public instance variables are variables that are declared within a class without any access modifier like 'private' or 'protected' or are explicitly declared as 'public'. These variables can be accessed from outside the class. To count them, you would scan through the class code and count any variable declarations that meet this criteria.