Sorting

Instead of defining a define the comparison function in the call to sort:

BGGA:

void sortBySalary(Collection<Employee> employees) {
    sort(employees,
        { 
          Employee e1, Employee e2
          => e1.getSalary().compareTo(e2.getSalary())
        }
    );
}

FCM:

void sortBySalary(Collection<Employee> employees) {
    Collections.sort(employees,
          #(Employee e1, Employee e2) {
            return e1.getSalary().compareTo(e2.getSalary());
          }
    );
}

CICE:

void sortBySalary(Collection<Employee> employees) {
    Collections.sort(employees,
       Comparator<Employee>(Employee e1, Employee e2) {
         return e1.getSalary().compareTo(e2.getSalary());
       }
    );
}

First class functions:

void sortBySalary(Collection<Employee> employees) {
    Function f = this.class.compare();
    Collections.sort(employees, f);
}


int compare(Employee e1, Employee e2) {
    return e1.getSalary().compareTo(e2.getSalary());
}