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//X is a supper class of Y and Z which are siblings. 
class X{} 
class Y extends X{} 
class Z extends X{} 
public class RunTimeCastDemo{ 
 public static void main(String args[]){ 
  X x = new X(); 
  Y y = new Y();       
  Z z = new Z();       
  X xy = new Y();   // compiles ok  
  X xz = new Z();   // compiles ok  
  Y yz = new Z();   // incompatible type (siblings), error 
  Y y1 = new X();   // X is not a Y, error 
  Z z1 = new X();    // X is not a Z, error 
           
  X x1 =  y;        // compiles ok (y is subclass of X), upcast 
  X x2 =  z;        // compiles ok (z is subclass of X), upcast 
  Y y1 = (Y) x;     // compiles ok but produces runtime error 
  Z z1 = (Z) x;     // compiles ok but produces runtime error 
  Y y2 = (Y) x1;    // compiles and runs ok (x1 is type Y), downcast 
  Z z2 = (Z) x2;    // compiles and runs ok (x2 is type Z), downcast 
  Y y3 = (Y) z;     // inconvertible types (siblings), error 
  Z z3 = (Z) y;      // inconvertible types (siblings), error 
  Object o  = z; // OK, upcast 
  Y o1 = (Y) o;  // compiles ok but produces runtime error 
 } 
}