Android - Compare custom object by multiple fields (different object/primitive types)

Question

How would you compare a custom object by a String field and an int field?

For example:

public class person implements Comparable<Person> {

    String name;
    int age;

    @Override
    public int compareTo(@NonNull Person another) {
        return name.compareToIgnoreCase(another.name);
    }
}

As you can expect, this works well and sorts the person objects in ascending order by name.

My problem: I also want to sort the list of Person objects by their age as well.

When it is sorted, the List should look like this:

name = a, age = 18
name = b, age = 18
name = c, age = 18
name = a, age = 20
name = b, age = 20
name = c, age = 20
...and so on...

Answer 1

First, check your primary attributes. If these are equal, check the secondary attributes:

@Override
public int compareTo(@NonNull Person another) {
    int result = Integer.compare(age, another.age);
    if (result == 0) {
        result = name.compareToIgnoreCase(another.name);
    }
    return result;
}

---

For pre-1.7 Java versions – the manual way:

@Override
public int compareTo(@NonNull Person another) {
    if (age == another.age) {
        return name.compareToIgnoreCase(another.name);
    } else if (age < another.age) {
        return -1;
    } else {
        return 1;
    }
}