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 + "}";
    }
}