Set JDialog width according to the size of the column sums of a table

I have the sum of the width of the columns and I need to set this value so that it does not hide parts of the columns and decrease the window. Any suggestion?  I created a method that returns the sum of the size of the columns.  Then I made another method to add this value to the one in the window.

 public void autoSetLargura(List<Integer> colunas){
            Integer soma = getTabelaUtils().setPreferredWidthJanelaColunas(colunas)  + 300;

            this.setPreferredSize(new Dimension(soma, 500));

 }



     public Integer setPreferredWidthJanelaColunas(List<Integer> lista) { 
     //seta as colunas e me retorna a soma delas.
                Integer somaColunas = 0;
                for (int i = 0; i < lista.size(); i++) {
                    setPreferredWidthColuna(i, lista.get(i));
                    somaColunas +=lista.get(i);
                }
                return somaColunas;
     }

These are methods, using the pack () it resizes right, but I have to do this on all windows of the same type, as the same has a base, doing on this basis it would work for all that implement it.