Instance Variables

BankAccount.java

private int balance; // current balance in cents

The next logical step are the private instance variables of a class.

Some guidelines:

Include only variables that describe an instance of that class. Leave out temporary variables as these can be better put into the methods of a class.

Meaningful names should be selected that provide a reader with an initial idea of its semantics.

Add a comment that specifies the variable in more detail: How is a value encoded (in the example above we represent a balance in cents) and which role does it play?

Specify the relationships between the instance variables of a class, if there are some.