The

COMPOSITION

Relationship

• A relationship that exists between objects
  
• In this relationship "the whole" object always has a "the part" object
  
• In fact "the part" object is called (made) in "the whole's" constuctor method. Insuring it is made whenever "the whole" is called.
  
• Click here to see it in Java code

Lets say you were modeling a classroom. Now every classroom needs a teacher. However to model the teacher in the classrooms constuctor method is too rigid. So we make an instance variable before the constuctor method to represent the teacher, and since it's an instance variable it can be used thoughout the classroom class. Then in the Classrooms constuctor we assign a new teacher to this variable.