ERROR - The method sort(Comparator) in the type List<[Integer]> is not applicable for the arguments ()

Error

The method sort(Comparator<? super [Integer]>) in the type List<[Integer]> is not applicable for the arguments ()

Error Type

Compile Time ( Java 8 )

Sample Code

List<Integer> intList = new ArrayList<Integer>();
intList.add(6);
intList.add(5);
intList.sort();

Cause

The method sort expects the argument of the type Comparator.

Possible Resolution

Specify the Comparator using Lambda Expression

List<Integer> intList = new ArrayList<Integer>();
intList.add(6);
intList.add(5);
intList.sort((i,j)->i.compareTo(j));

or Specify null for natural order sorting.

List<Integer> intList = new ArrayList<Integer>();
intList.add(6);
intList.add(5);
intList.sort(null);