Composition

A class can contain simple variables as data fields, and it can contain objects of another class as data fields. For example, you might create a class named Date that contains a month, day, and year, and add two Date fields to an Employee class to hold the Employee ’s birth date and hire date. Then you might create a class named Department that represents every department in a company, and create the Department class to contain a supervisor, who is an Employee .
Figure 11- 11 contains a diagram of these relationships. When a class contains objects of another class, the relationship is called a whole-part relationship or composition . The relationship created is also called a has-a relationship because one class “has an” instance of another—for example, a Department has an Employee and an Employee has a hire Date .

does a composition is called an is-a relationship because one class "is an" instance of another?

additional info: A class can contain objects of another class as data fields.

additional info: Composition occurs when you use an object as a field within another class.

Anna06 wrote:does a composition is called an is-a relationship because  one class "is an" instance of another?

Composition is called a has-a relationship because one class "has an" instance of another.

Anna06 wrote:additional info: A class can contain objects of another class as data fields.

why?

it is related to database?