public static Map<String,Integer> processData(ArrayList<String> array) {

List<Emp> empList = array.stream().map(s->toEmp.apply(s)).collect(Collectors.toList());

Map<String,Optional<Emp>> r = empList.stream().collect(

Collectors.groupingBy(Emp::getDepartment,Collectors.maxBy((e1,e2)-> e1.getID().compareTo(e2.getID()))));

Map<String,Integer> retVal = new HashMap<>();

r.forEach((k,v) -> retVal.put(k,v.get().getSalary()));

return retVal;

}

public static void main(String[] args) {

String fileName = "input.txt";

System.out.println(processData(getfileContent(fileName)));

}

private static ArrayList<String> getfileContent(final String fileName) {

URL url = DataOperation2.class.getClassLoader().getResource(fileName);

ArrayList<String> lines = new ArrayList<>(100);

try (Stream<String> stream = Files.lines(Paths.get(url.toURI()))) {

stream.forEach(lines::add);

} catch (IOException | URISyntaxException e) {

e.printStackTrace();

}

return lines;

}

static Function<String,Emp> toEmp = ln -> {

String[] empArr = ln.split(",");

Emp e = new Emp();

e.setID(Integer.valueOf(empArr[0].trim()));

e.setName(empArr[1]);

e.setDepartment(empArr[2]);

e.setSalary(Integer.valueOf(empArr[3].trim()));

return e;

};

private Integer ID;

private String Name;

private String Department;

private Integer Salary;

public Integer getID() {

return ID;

}

public void setID(Integer iD) {

ID = iD;

}

public String getName() {

return Name;

}

public void setName(String name) {

Name = name;

}

public String getDepartment() {

return Department;

}

public void setDepartment(String department) {

Department = department;

}

public Integer getSalary() {

return Salary;

}

public void setSalary(Integer salary) {

Salary = salary;

}

}