if  (type == XXX. class ) {
     XXX val = (XXX)some_varible
    doSmth(val);
} 
 else  
 if  (type == YYY. class ) {
     YYY val = (YYY)some_varible
    doSmth(val);
}  ...

 public   void  <T>cast() {
   T val = (T)some_varible;
    doSmth(val);
}

 public   void  cast( Class  type) {
     if  (type.isAssignableFrom(some_varible.getClass())) {
          Method m = type.getMethod(...bla-bla-bla...);
          Object result = m.invoke(some_varible, ...bla-bla-bla...);
          ... use result here ...
    }  else  {
        throw   new  ClassCastException("Don't do it, pls.");
    }
}