Générer un char, avec la fréquence d'apparition des lettres

import java.util.Random;

public enum Letter
{
    A(158), B(19), C(67), D(76), E(304), F(22), G(18), H(15), I(155),
    J(11), K(1), L(113), M(61), N(147), O(111), P(62), Q(28), R(135),
    S(164), T(150), U(130), V(34), W(2), X(8), Y(6), Z(3);
    
    private final int occ;
    
    private Letter(int occ)
    {
        this.occ = occ;
    }
    
    private static char[] tab = null;
    
    private static void fillTab()
    {
        int n = 0;
        
        for (Letter v : Letter.values())
            n += v.occ;
        
        tab = new char[n];
        
        int i = 0;
        for (Letter v : Letter.values())
            for (int j = 0; j < v.occ; i++ , j++ )
                tab[i] = v.toString().charAt(0);
    }
    
    public double getFrequency()
    {
        if (tab == null)
            fillTab();
        
        return ((double) occ) / tab.length;
    }
    
    private static Random rand = new Random();
    
    public static char random()
    {
        if (tab == null)
            fillTab();
        
        return tab[rand.nextInt(tab.length)];
    }
}

public class Test
{
    public static void main(String[] args)
    {
        System.out.println(Letter.A.getFrequency()); // 0.079
        
        for (int i = 0; i < 10; i++ )
            System.out.print(Letter.random());
    }
}