Designing a Class

One of the advantages of object-oriented design is that it allows a programmer to create a new data type that is reusable in other situations.

When designing a new class, three components must be identified — attributes, behaviors, and constructors. To determine attributes of a class, look at the nouns associated with that object. To determine behaviors, look at the verbs.

Real-world connections

Let’s consider a checking account at a bank.

The account would need to record such things as:

• the account number
• the current balance
• the type of checking account it is, etc (these are nouns).

These would be the attributes of the checking account.

It would also need to be able to do certain actions, such as:

• withdrawing
• depositing money (these are verbs).

These would be the behaviors of the checking account.

Finally, the checking account object needs to be created in order to be used, so the class must define how the creation process works. This is accomplished in the constructors.