What is the difference between aggregation and composition in java

The difference between aggregation and combination is: aggregation represents a has-a relationship, a one-way relationship; the two classes (or entities) in the aggregation can exist independently and will not affect each other. The combination represents a part-of relationship. The two entities (or classes) in the combination are highly dependent on each other and will affect each other.

This article will introduce to you association, aggregation and combination in Java, so that you can understand the difference between aggregation and combination. I hope it will be helpful to you. [Recommended related video tutorials: Java Tutorial]

What is the association in java?

Association is a relationship between two independent classes that can connect two completely independent entities through their objects (or instances). Associations can be of any type, one-to-one, one-to-many, many-to-one, many-to-many.

What is aggregation in java?

Aggregation is a special form of association that represents a has-a relationship; it is a one-way relationship between classes (or entities). For example: wallet and money, the wallet will contain money, but the money will not contain the wallet; this is a naturally one-way relationship.

In an aggregation relationship, two classes (or entities) can exist independently and will not affect each other; that is to say: the existence of one class (or entity) will not affect the other classes (or entities) aggregated with it. The existence or absence of the class.

What is combination in java?

A combination is a restricted form of aggregation that represents a part-of relationship; two entities (or classes) are highly dependent on each other. Just like: humans and the heart, humans need the heart to survive, and the heart also needs the human body to survive.

In other words, when classes (entities) depend on each other and their lifespan is the same (if one dies, then the other dies too), then it is a composition. For example: without humans, the heart would have no meaning.

The difference between aggregation and combination

##1. Difference in dependencies

The two classes (or entities) in an aggregation can exist independently and will not affect each other; the associated party can be independent of the associated party, and the dependence does not powerful.

On the contrary, the two entities (or classes) in the combination are highly dependent on each other, and they will affect each other.

2. Differences in relationship types

Aggregation represents a has-a relationship, a one-way relationship; combination represents a part-of relationship.

3. Differences in association strength

Aggregation is a weak association; combination is a strong association.

4. Differences in life cycles

The life cycles of the two classes (or entities) in the aggregation relationship are not synchronized; however, in the combination relationship The life cycles of two classes (or entities) are synchronized.

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