Properly removing an Integer from a List<Integer>

Solution 1:

Java always calls the method that best suits your argument. Auto boxing and implicit upcasting is only performed if there's no method which can be called without casting / auto boxing.

The List interface specifies two remove methods (please note the naming of the arguments):

• remove(Object o)
• remove(int index)

That means that list.remove(1) removes the object at position 1 and remove(new Integer(1)) removes the first occurrence of the specified element from this list.

Solution 2:

You can use casting

list.remove((int) n);

and

list.remove((Integer) n);

It doesn't matter if n is an int or Integer, the method will always call the one you expect.

Using (Integer) n or Integer.valueOf(n) is more efficient than new Integer(n) as the first two can use the Integer cache, whereas the later will always create an object.