List's remove method is raw

Question

The question says it all..

From List's code:

Add method: public boolean add(E e) { ... }

Whereas, remove method: public boolean remove(Object o) { .. }

Is there any specific reason for this?

Answer 1

From the javadoc :

If this list does not contain the element, it is unchanged

So adding a type constraint here would be simply useless, while the constraint on add ensures at compile time the list contains what is written on the box.

Note that there is some liberty for implementation as the method is allowed to throw a

ClassCastException if the type of the specified element is incompatible with this list (optional)

The ArrayList implementation doesn't throw this exception :

439    public boolean remove(Object o) {
440         if (o == null) {
441             for (int index = 0; index < size; index++)
442                 if (elementData[index] == null) {
443                     fastRemove(index);
444                     return true;
445                 }
446         } else {
447             for (int index = 0; index < size; index++)
448                 if (o.equals(elementData[index])) {
449                     fastRemove(index);
450                     return true;
451                 }
452         }
453         return false;
454     }

This means you don't have to check the class of raw objects before you do the remove operation.