Not quite. Barring is a dominant gene--if a chicken has the gene, the chicken will be barred. I suppose a buff bird with barring might not be noticed, but barring on a black bird shows up quite clearly.
Were there any barred roosters that could have mated with the same hens? If so, then you...
If the mother had barring and the father did not, then all barred chicks are cockerels. (It's the method used to create black sexlinks, and it works because barring is on the Z sex chromosome: the mother passes her Z chromosome to her sons only, not to her daughters.)
Sorry to bring bad news, but since the Ayam Cemani was the father, all barred chicks are males. (Just like with the more common types of Black Sexlinks: barred mother gives barred sons, not-barred father gives not-barred daughters.)
Solid black chicks may be female (Barred Rock mother), or...