Sorting a Custom Class Array List String Using Collections.sort Command
I'm trying to sort my own list of arrays of classes using Collections.sort by declaring my own anonymous comparator. But sorting doesn't work as expected.
My code
Collections.sort(arrlstContacts, new Comparator<Contacts>() {
public int compare(Contacts lhs, Contacts rhs) {
int result = lhs.Name.compareTo(rhs.Name);
if(result > 0)
{
return 1;
}
else if (result < 0)
{
return -1;
}
else
{
return 0;
}
}
});
The result is not in sorted order.
As Adam says, just do:
Collections.sort(
arrlstContacts,
new Comparator<Contacts>()
{
public int compare(Contacts lhs, Contacts rhs)
{
return lhs.Name.compareTo(rhs.Name);
}
}
);
The method String.compareTo
does a lexicographic comparison, which your original code denies. For example, strings number1
and number123
when compared will produce -2 and 2, respectively.
By simply returning 1, 0, or -1, there is a chance (as it is for you) that the merge portion of the merge sort used by the method Collections.sort
may not be able to distinguish enough between the strings in the list, resulting in a list that is not sorted alphabetically.
As pointed out by Adam, you can use return (lhs.Name.compareTo(rhs.Name));
likeso:
Collections.sort(arrlstContacts, new Comparator<Contacts>() {
public int compare(Contacts lhs, Contacts rhs) {
return (lhs.Name.compareTo(rhs.Name));
}
});