I have an ArrayList of ArrayList of Bean and I need to sort this ArrayList according to the date variable in Bean.
ArrayList<ArrayList<DriverLogDatePair>> driverLogList
And DriverLogDatePair bean have a variable DateTime date, it also has a compareTo method.
public int compareTo(DriverLogDatePair o) {
return date.compareTo(o.date);
}
But I am not able to sort driverLogList.
You have to complete this code:
ArrayList<ArrayList<DriverLogDatePair>> driverLogList = new ArrayList<>();
Collections.sort( driverLogList, new Comparator<ArrayList<DriverLogDatePair>>(){
@Override public int compare(
ArrayList<DriverLogDatePair> left,
ArrayList<DriverLogDatePair> right )
{
return 0;
}});
Because the first array contains an array which contains a Comparable. The comparator you provide is for DriverLogDatePair not for ArrayList< DriverLogDatePair >
(... After comments of this post... )
At your request, to complete the comparator I suggest:
int size = left.size();
int diff = size - right.size();
if( diff != 0 ) return diff;
for( int i = 0; i < size; ++i ) {
diff = left.get( i ).compareTo( right.get(i) );
if( diff != 0 ) return diff;
}
But I have no idea of the true meaning of this comparison. It's a semantic problem, is this really what you want?
The problem is that if you sort driverLogList it tries to compare the contained ArrayList objects. I would write a wrapper for that list:
public class DriverLogDatePairList extends ArrayList<DriverLogDatePair> implements Comparable<DriverLogDatePairList> {
public int compareTo(DriverLogDatePairList o) {
//your comparison criteria
}
}
Then you can use it this way and sort it:
ArrayList<DriverLogDatePairList> driverLogList;
Generally, you can sort Lists using
Collections.sort( list , comparator )
So, assuming you want to sort the inner lists, iterate through the outer list and use that construct to sort the elements, after having implemented a fitting comparator:
Comparator comparator =
new Comparator<DateTime>()
{
@Override
public int compare( DateTime o1, DateTime o2 )
{
return o1.compareTo( o2 );
}
}
Cheers,
Your compare method is seems wrong to me..
it should be like: (here i am assuming date as DriverLogDatePair Object )
public int compareTo(DriverLogDatePair o) {
if(date.date < o.date) return -1;
else if (date.date < o.date) return 0;
else return 1;
}
ArrayListdo you want to sort, the inner or outer one? You have a list of lists and you want to sort on a date element in the inner list, so I assume you want to sort the inner lists - or what?ArrayList<DriverLogDatePair>? If second, what criteria you want to use?comparatorand use it with theCollection.sort(list,newcomparator)method