import java.util.*;

class Employee {
    private int empNo;
    private String name;
    private Set<String> skills;

    public Employee(int empNo, String name, Set<String> skills) {
        this.empNo = empNo;
        this.name = name;
        this.skills = new HashSet<>(skills); // defensive copy
    }

    public int getEmpNo() {
        return empNo;
    }

    public String getName() {
        return name;
    }

    public Set<String> getSkills() {
        return new HashSet<>(skills); // return copy to maintain immutability
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (!(o instanceof Employee)) return false;
        Employee employee = (Employee) o;
        return empNo == employee.empNo &&
               Objects.equals(name, employee.name) &&
               Objects.equals(skills, employee.skills);
    }

    @Override
    public int hashCode() {
        return Objects.hash(empNo, name, skills);
    }

    @Override
    public String toString() {
        return "Employee{empNo=" + empNo + ", name='" + name + "', skills=" + skills + "}";
    }
}

public class EmployeeMapExample {
    public static void main(String[] args) {
        Employee emp1 = new Employee(1001, "Alice", Set.of("Java", "Spring", "SQL"));
        Employee emp2 = new Employee(1002, "Bob", Set.of("Python", "Django", "ML"));
        Employee emp3 = new Employee(1003, "Charlie", Set.of("JavaScript", "React", "Node.js"));

        Map<Employee, String> employeeRoles = new HashMap<>();
        employeeRoles.put(emp1, "Backend Developer");
        employeeRoles.put(emp2, "Data Scientist");
        employeeRoles.put(emp3, "Frontend Developer");

        // Display all employee-role mappings
        for (Map.Entry<Employee, String> entry : employeeRoles.entrySet()) {
            System.out.println(entry.getKey() + " -> " + entry.getValue());
        }
    }
}