What is displayed on the console when running the following program?

What is the type of the following lambda expression?

i -> 2 * i

Which of the following operations is correct if 
List<String> l1 = new ArrayList<String>?

Which of the following specify a comparator for strings in increasing order of their length?

Which of the following collections cannot contain duplicate elements?

What will be displayed on the console when running the following code?

ArrayList<Integer> l1 = new ArrayList<>();
l1.add(1); 
l1.add(2); 
l1.add(3);
l1.remove(2);
System.out.println(l1);

What is the result of compiling and (possibly) executing the following class?

What is displayed on the console when running the following program?

What is the output of the following program?

What is the output of running class Main?