Why cannot cast Integer to String in java?

Question

Why this is not possible:

Because String and Integer are not in the same Object hierarchy.

      Object
     /      \
    /        \
String     Integer

The casting which you are trying, works only if they are in the same hierarchy, e.g.

      Object
     /
    /
   A
  /
 /
B

In this case, (A) objB or (Object) objB or (Object) objA will work.

Hence as others have mentioned already, to convert an integer to string use:

String.valueOf(integer), or Integer.toString(integer) for primitive,

or

Integer.toString() for the object.