Sort an ArrayList base on multiple attributes
Implement a custom Comparator
, then use Collections.sort(List, Comparator)
. It will probably look something like this:
public class FooComparator implements Comparator<Foo> {
public int compare(Foo a, Foo b) {
int dateComparison = a.date.compareTo(b.date);
return dateComparison == 0 ? a.value.compareTo(b.value) : dateComparison;
}
}
Collections.sort(foos, new FooComparator());
Java-8 solution using Stream API:
List<Foo> sorted = list.stream()
.sorted(Comparator.comparing(Foo::getDate)
.thenComparing(Foo::getValue))
.collect(Collectors.toList());
If you want to sort the original list
itself:
list.sort(Comparator.comparing(Foo::getDate)
.thenComparing(Foo::getValue));
public static <T> void sort(List<T> list, final List<Comparator<T>> comparatorList) {
if (comparatorList.isEmpty()) {//Always equals, if no Comparator.
throw new IllegalArgumentException("comparatorList is empty.");
}
Comparator<T> comparator = new Comparator<T>() {
public int compare(T o1, T o2) {
for (Comparator<T> c:comparatorList) {
if (c.compare(o1, o2) > 0) {
return 1;
} else if (c.compare(o1, o2) < 0) {
return -1;
}
}
return 0;
}
};
Collections.sort(list, comparator);
}
If you want sample code looks like, you can use following:
Collections.sort(foos, new Comparator<Foo>{
public int compare(Foo a, Foo b) {
int dateComparison = a.date.compareTo(b.date);
return dateComparison == 0 ? a.value.compareTo(b.value) : dateComparison;
}
});