Sorting numeric String interval in java

Question

I'm having an Person class with some Person and there details as there name, age band.
The ageband interval is {"0-5", "6-10", "11-30","31-45", "46-50","50-100", "100-110"};

I'm having a Person class with name , ageBand String interval and it's parameterised constructor, getters, setters.

class Person {
    String name;
    String ageBand; //say it is string "0-50" which i pass in constructor while creating a person.
    //getters
    //setters
}

class TestAgeBand {
    public static void main(String args[]) {
        ArrayList<Person> person = new ArrayList<Person>();

        Person p1 = new Person("Mike1", "0-5");   
        Person p2 = new Person("Mike2", "6-10");
        Person p3 = new Person("Mike3", "11-30");   
        Person p4 = new Person("Mike4", "31-45");   
        Person p5 = new Person("Mike5", "50-100");   
        Person p6 = new Person("Mike6", "46-50"); 
        Person p7 = new Person("Mike7", "100-110");

        person.add(p1);
        //adding all persons to list.
    }
}

Here's what I'm doing with my code to sort the interval. I need to sort persons according to increasing intervals. I'm using Treemap to sort the intervals.

Map<String, Person> ageBandMap = new TreeMap<String, Person>(){
    for(Person p: person) {
        ageBandMap.put(p.ageBand, p.name);
    }
}

When I print interval keyset, I get

Output:

[0-5, 100-110, 11-30, 31-45, 46-50, 50-100, 6-10]

Which I don't need. I need intervals sorted like this:

[0-5, 6-10, 11-30, 31-45, 46-50, 50-100, 100-110]

Answer 1

Try splitting the your ageBand string and converting it into an Integer, it will be easier to sort.

person.stream().sorted(Comparator.comparing(element -> Integer.parseInt(element.getAgeBand().split("-")[0])))
            .collect(Collectors.toList());

If you don't want to use Java 8, you can do it with Collections.sort() method.

 Collections.sort(person, new Comparator<Person>() {
        @Override
        public int compare(Person o1, Person o2) {
            return Integer.parseInt(o1.getAgeBand().split("-")[0]) - Integer.parseInt(o2.getAgeBand().split("-")[0]);
        }
    });