Java Sort List of Lists
Improved MartinS answer using Java 8 stream API
possiblePoles = possiblePoles.stream().sorted((o1,o2) -> {
for (int i = 0; i < Math.min(o1.size(), o2.size()); i++) {
int c = o1.get(i).compareTo(o2.get(i));
if (c != 0) {
return c;
}
}
return Integer.compare(o1.size(), o2.size());
}).collect(Collectors.toList());
You will have to implement your own Comparator
class and pass in an instance to Collections.sort()
class ListComparator<T extends Comparable<T>> implements Comparator<List<T>> {
@Override
public int compare(List<T> o1, List<T> o2) {
for (int i = 0; i < Math.min(o1.size(), o2.size()); i++) {
int c = o1.get(i).compareTo(o2.get(i));
if (c != 0) {
return c;
}
}
return Integer.compare(o1.size(), o2.size());
}
}
Then sorting is easy
List<List<Integer>> listOfLists = ...;
Collections.sort(listOfLists, new ListComparator<>());
For this example [[1, 3], [1, 2]], if you want to sort the list by both elements you can use sorted from Java 8 manually implemented the comparator method, validating all cases like the following example:
List<List<Integer>> result = contests.stream().sorted((o1, o2) -> {
if (o1.get(1) > o2.get(1) ||
(o1.get(1).equals(o2.get(1)) && o1.get(0) > o2.get(0))) {
return -1;
} else if (o1.get(1) < o2.get(1) ||
(o1.get(1).equals(o2.get(1)) && o1.get(0) < o2.get(0))) {
return 1;
}
return 0;
}).collect(Collectors.toList());
OR
contests.sort((o1, o2) -> {
if (o1.get(1) > o2.get(1) ||
(o1.get(1).equals(o2.get(1)) && o1.get(0) > o2.get(0))) {
return -1;
} else if (o1.get(1) < o2.get(1) ||
(o1.get(1).equals(o2.get(1)) && o1.get(0) < o2.get(0))) {
return 1;
}
return 0;
});