When should you use instance variables, parameters, and local variables? List at least one mistake that you can make when misusing one type of variable for another.
What will be an ideal response?
The only reason to use an instance variable is to store information within an object. The
only reason to use a parameter is to transmit information to a method. The only reason to use a local variable is for temporary working storage within a method. A very common mistake is to misuse one kind of variable for another.
Parameters are preferable over instance variables because: if several methods share a pool of variables, and one method misuses a variable, other methods can be affected; it is easier to understand methods and the relationships between them when communications are explicitly defined in terms of parameters and return values; methods that are passed parameters can be reused in many situations.
Common mistakes include:
1. Instance variable used for temporary working storage.
2. Local variable used to remember information in an object.
3. Method accesses data by directly referencing an instance variable when it could use a parameter instead.
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