java quicksort multiple criteria

Question

I would like to use quicksort to sort my objects. The object named Person contains two fields (firstname and lastname).
class Person { private firstName; private lastName; //+getter/setter }
It should be sorted by last name and if last name are same, then by first name. So if I have Persons ["Miller","Tom"; "Smith","Jerry", "Miller", "Alex"] the output must be "Miller", "Alex"; "Miller","Tom", "Smith","Jerry". Sorting by last name works, but I don't know how to realize the second part.

Here the code snippet:
public void quicksort (List<Person> records, int left, int right) { int index = partition(records, left, right); if (left < index - 1) { quicksort (records, left, index - 1); } if (index < right) { quicksort (records, index, right); } }

public int partition(List<Person> records, int left, int right) {
int i = left, j = right;
Person tmp;
Person pivot = records.get(left);

while (i <= j) {
    while (records.get(i).getLastName().compareTo(pivot.getLastName()) < 0) {
        i++;
    }
    while (records.get(j).getLastName().compareTo(pivot.getLastName()) > 0) {
        j--;
    }
    //TODO: here I need something like if last name same, compare first name
    if (i <= j) {
        // swap elements
        tmp = records.get(i);
        records.set(i, records.get(j));
        records.set(j, tmp);
        i++;
        j--;
    }
}

return i; }
Any Idea?

Answer 1

Define the compareTo method for your Person class. Compare last name, if they match, then first name:

public int compareTo(Person to) {
  int cmp = this.lastName.compareTo(to.lastName);
  if (cmp == 0)
    cmp = this.firstName.compareTo(to.firstName);
  return cmp;
}

Then you got:

while (records.get(j).compareTo(pivot) > 0) {