Cohesion

Cohesion in computer programming is the degree to which the elements of a certain module (class in our case) belong together.

Thus, cohesion measures the strength of relationship between pieces of functionality within a given module.

Simply, all the related code should be close to each other.

Cohesion is usually described as:

• High Cohesion
• Low Cohesion

High Cohesion

Modules with high cohesion tend to be preferable, because high cohesion is associated with several desirable qualities of software including:

• Robustness
• Reliability
• Reusability
• Understandability

High cohesion means that class should do one thing and one thing very well.

Low Cohesion

Low cohesion is associated with several undesirable qualities such as:

• Being difficult to maintain
• Difficult to test
• Difficult to understand

Conclusion

High cohesion and low coupling give us better designed code that is easier to maintain.