Open/Closed Principle

Open/Closed Principle
Software entities should be open for extension, but closed for modification. This avoids side-effects through changes. This can be relaized by utilizing inheritance. In combination with Liskovs Substitution Principle, overwritten methods do not change behavior, but the execution algorithm. You can find this principle easily in UML class diagrams, when looking for inheritance.

public class Calculator {
    public Super (ServiceA serviceA, ServiceB serviceB, ServiceC serviceC) {
        this.serviceA = serviceA;
        // …
    }
}

The opend/closed principle is utilized by inheritance:

public class BusinnessCalculator extends Calculator {
    public BusinnessCalculator (ServiceA serviceA, ServiceB serviceB, ServiceC serviceC) {
        super (serviceA, serviceB, serviceC);
            // …
        }
    }
}