I have an ArrayList<List<String>>
and im trying to use the built-in binary search in the collection but I always come up with an error
int index = Collections.binarySearch(arraylistdata, id);
Where arraylistdata is my ArrayList
of List<String>
.
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Answer
public class CollectionsTest { @Test void test() { List<String> list = List.of("a", "b", "c"); int index = Collections.binarySearch(list, "b"); Assertions.assertEquals(1, index); } }
This works fine, but you need to known that Collections#binarySearch
accept a List<? extends Comparable<? super T>>
as its first parameter.
While in your case, ArrayList<List<String>>
does not match the requirement , as List<String>
or List<?>
itself is not a Comparable
object.