Questions and Answers
What is association?
If one class uses or requires features of another class then they are 'associated'.
What types of associations are there?
Dependency, composition, and aggregation.
What is dependency?
When one class 'uses' another class internally.
Where do dependencies most often exist? Provide an example.
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What's the difference between composition and aggregation?
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What is composition?
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What is a common way to decide if something is composition? Provide an example.
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What is aggregation?
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What is multiplicity? Provide an example.
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What's the delegation principle?
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What is a delegation method for adding used with aggregation? Provide an example.
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What is a delegation method for removing used with aggregation? Provide an example.
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What is a delegation method for finding the size of an array used with aggregation? Provide an example.
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Study Notes
Association
- Association occurs when one class utilizes or depends on features of another class.
Types of Associations
- Key types of associations include dependency, composition, and aggregation.
Dependency
- Dependency arises when one class utilizes another class internally.
- Involves a class using one or more objects from another class type.
Location of Dependency
- Dependencies usually occur within methods where objects of another class are either passed as parameters or locally declared.
- Example: A class may contain a method that utilizes the Math class for calculations.
Composition vs. Aggregation
- Composition indicates a single object of another class is stored within a class.
- Aggregation indicates a collection of objects from another class is held by a class.
Composition
- Composition involves a class being made up of one or more other classes, possessing fields of another class type.
Identifying Composition
- Look for "has-a" relationships to determine composition; for example, “An Employee has-a Name and a Date of employment.”
Aggregation
- Aggregation is used when a class serves as a container for holding collections of objects.
Identifying Aggregation
- Common identification points for aggregation and examples are unspecified in the notes.
Declaring Aggregation Class
- Details regarding the declaration of an aggregation class are unspecified in the notes.
Multiplicity
- Definition and examples related to multiplicity are not provided.
Aggregation Example
- Specific examples of aggregation are not given.
Delegation Principle
- Delegation allows classes to use or store objects, thereby reusing methods of those objects.
- Common in both composition and aggregation but more prevalent with aggregation.
Implementation of Aggregation
- Specifics regarding the implementation of aggregation classes are not provided.
Delegation Method for Adding
- An example of a delegation method for adding could be a method called
addSongto manage a list calledsonglist.
Delegation Method for Removing
- Provides a way to remove items using a delegation method, although details on implementation are not included.
Delegation Method for Finding Size
- Discusses a method for determining the size of an array through a delegation method like
addSongand relating it tosonglist, but details are absent.
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Description
Test your understanding of association, dependency, composition, and aggregation in object-oriented programming. This quiz focuses on the key concepts covered in Lecture 6, ensuring you grasp the fundamental relationships between classes. Perfect for reviewing the module's content and enhancing your programming vocabulary.
