Casting Object References with Collections : Reference Type Casting « Type Casting « SCJP






  1. SCJP
  2. Type Casting
  3. Reference Type Casting
import java.util.Vector;

class MainClass {
  public static void main(String args[]) {
    String s1 = "abc";
    String s2 = "def";
    Vector v = new Vector();
    v.add(s1);
    s2 = (String) v.elementAt(0);
    System.out.println(s2);
  }
}








4.3.Reference Type Casting
4.3.1.Object reference conversion
4.3.2.An interface type can be converted to an interface type or to Object.
4.3.3.Convert interface to super-interface
4.3.4.Object Method-Call Conversion
4.3.5.Cast between an interface and a nonfinal object.
4.3.6.Runtime casting: the class being converted must be itself or must inherit from it.
4.3.7.If New type is an interface, the class of the expression being converted must implement New type.
4.3.8.For = with object references, if the type of the left operand is a class C, then the type of the right operand must be a subclass of C or the null value.
4.3.9.If the type of the left operand is an interface I, the type of the right operand must be a subinterface of I, or a class that implements I, or the null value.
4.3.10.A reference to any object can be cast into a reference to an object of class Object.
4.3.11.A reference to an object can be cast into a reference to an object of its parent class.
4.3.12.A reference to an object can be cast into a reference to an object of its implemented interface
4.3.13.A reference to an object can be cast into a reference to an object of its implemented super interface
4.3.14.Casting Object References with Collections
4.3.15.An Object reference can be converted to:
4.3.16.Use a reference variable to refer to any object that is a subclass of the declared reference variable type