A payroll system modification which is a Java-based program designed to manage different types of employees and calculate their earnings based on their employment category. The system uses object-oriented programming (OOP) principles such as inheritance, polymorphism, and abstraction to handle various employee types, including salaried employees, hourly employees, commission employees, base-pluscommission employees, and piece workers. The program demonstrates how different employee classes can extend a common superclass while implementing their own earnings calculation logic. Additionally, it showcases polymorphic processing by treating all employee objects uniformly while still executing their specific methods.