[Java] Collectors

Stream<Employee> emps = ...

TreeSet<Employee> tree = emps.collect(
    Collectors.toCollection(
        () -> new TreeSet<Employee>(
            Comparator.comparingInt(Employee:getSalary)
    )
);

Stream<Employee> emps = ...

Map<String, Integer> salaries = emps.collect(
    Collectors.toMap(Employee::getName, Employee::getSalary)
);

Stream<Employee> emps = ...

Map<Integer, List<Employee>> brackets = 
    emps.collect(Collectors.groupBy(
        e -> e.getSalary()/1000
    )
);