Why we does not have List.contains(E o) List.remove(E o)

Question

List class is having
bool contains(Object o)
bool remove(Object o)
I was wondering why the List class doesn't have
bool contains(Object o)
bool remove(Object o)
Isn't user will not protected by compiler if they try to do some wrong stuff?
List<String> list = new ArrayList<String>();
list.remove(new Integer(123)); // I expect compiler to prevent us to do this???
Thanks!
Cheok

Answer 1

Peter__Lawrey wrote:
KwangHooi wrote:
Isn't user will not protected by compiler if they try to do some wrong stuff?User's should be protected, but developers need to understand what they are doing.
List<String> list = new ArrayList<String>();
list.remove(new Integer(123)); // I expect compiler to prevent us to do this???That assumes this is an error. The compiler could only determine trivial, pointless cases.
As a developer you need to be able to determine much more complex cases than the compiler ever could.I do not agree with you.
Generics feature in Java allow "a type or method to operate on objects of various types while providing compile-time type safety." When we mention about "compile-time type safety", we means the code may be compiled without errors and warnings and does not raise any unexpected ClassCastExceptions at runtime.
Cosider the following code before we are having generic feature :-
List v = new ArrayList();
v.add("test");
Integer i = (Integer)v.get(0);We will get java.lang.ClassCastException while trying to execute the third line. However, by using generic, programmers are protected from making mistake
List<String> v = new ArrayList<String>();
v.add("test");
Integer i = v.get(0);Compiling the third line of this fragment with J2SE 1.5 will yield a compile-time error because the compiler will detect that v.get(0) returns String instead of Integer.
So, a class designer, shall design the class in such a way that, "easy to be used, difficult to be mis-used"
Come back to the original question :-
If we already have a type safe
public boolean add(E e)
Why cann't we have
public boolean contains(E e)
public boolean remove(E e)