Give two profit of Reuse of Code.

Reusing the implementation. Place existing class directly inside a new class. The new class can be made up of any number and type of the other objects, in any grouping that is needed to achieve desired functionality. This idea is called composition (or generally, aggregation). Composition is often termed as "has-a" relationship or "part-of" relationship, as in "automobile has an engine" or "engine is part of automobile."

Reusing the interface. Take an existing class and make modifications to achieve required functionality. This concept is known as inheritance. The original class is called Base class or Parent class and modified class is called the Derived or Inherited or Sub or Child class.