Sort an ArrayList of Objects by last name, then first name
I have an arrayList of different types of players based on sports. I need to sort the list of players in the arrayList by last name to start. If 2 players have the same last name it needs to then sort those 2 players by the first name. example: Format Lastname firstname
Williams Robert
Phillips Warren
Doe John
Phillips Mark
Output should be
Doe John
Phillips Mark
Phillips Warren
Williams Robert
What I have now only sorts by either the first or last. I have it by last atm in my code.
public static void sortPlayers(ArrayList playerList) {
for (int i = 0; i < playerList.size(); i++) {
for (int j = 0; j < playerList.size(); j++) {
Collections.sort(playerList, new Comparator() {
public int compare(Object o1, Object o2) {
PlayerStats p1 = (PlayerStats) o1;
PlayerStats p2 = (PlayerStats) o2;
return p1.getPlayerLastName().compareToIgnoreCase(p2.getPlayerLastName());
}
});
}
}
}
Change the comparator to:
public int compare(Object o1, Object o2) {
PlayerStats p1 = (PlayerStats) o1;
PlayerStats p2 = (PlayerStats) o2;
int res = p1.getPlayerLastName().compareToIgnoreCase(p2.getPlayerLastName());
if (res != 0)
return res;
return p1.getPlayerFirstName().compareToIgnoreCase(p2.getPlayerFirstName())
}
Petar's answer is correct, just two remarks:
- Use
List
instead ofArrayList
as method argument, as the interface is more general, and the method will work even if you change to anotherList
type (likeLinkedList
... ) later - Use generics to make your code more type safe.
An improved version:
//the place where you define the List
List<PlayerStats> playerList = new ArrayList<PlayerStats>();
public static void sortPlayers(List<PlayerStats> playerList) {
Collections.sort(playerList, new Comparator<PlayerStats>() {
public int compare(PlayerStats p1, PlayerStats p2) {
int res = p1.getPlayerLastName().compareToIgnoreCase(p2.getPlayerLastName());
if (res != 0)
return res;
return p1.getPlayerFirstName().compareToIgnoreCase(p2.getPlayerFirstName())
}
});
}