Java cast base class to an extended class -

i have class used in project sort of field holder. like:

class {     private string field = null;     private string field2 = null;     private string field3 = null;      // , generic getters , setters }

in part of code need add additional fields class. did

class b extends {     private string fieldinb  = null;      // , getters , setters }

in function thought

public void foo( a ) {     b b = (b)a; }

and have fields written in aobject , set field in b , use it. seams common problem, don't know how except ugly approach:

public b( a ) {     // copy fields 1 @ time }

you use dozer. allows map bean property values 1 bean class another.

Chrom