code: public void setField(Object o, String fieldName, Object value)
        throws NoSuchFieldException, IllegalAccessException {
      
      Field field = o.getClass().getDeclaredField(fieldName);
      field.setAccessible(true);
      field.set(o, value);
    }
docs: Sets the specified field on Object o to the specified value, even if that field is not normally accessible.
  Only fields declared on the class for Object o can be accessed.
  
  @param o Object to access
  @param fieldName Name of field whose value will be set
  @param value Object value that will be set for the field
  @throws NoSuchFieldException if no field matches <code>fieldName</code>
  @throws IllegalAccessException
  @throws IllegalArgumentException if the type of <code>value</code> is incorrect