public static String currencyFormat(BigDecimal n) {
    return NumberFormat.getCurrencyInstance().format(n);
}

BigDecimal newBD = oldBD.setScale(2);

String displayString = oldBD.setScale(2).toPlainString();

DecimalFormat df = new DecimalFormat("#,###.00");
     System.out.println(df.format(new BigDecimal(123456.75)));
     System.out.println(df.format(new BigDecimal(123456.00)));
     System.out.println(df.format(new BigDecimal(123456123456.78)));

123,456.75
123,456.00
123,456,123,456.78

BigDecimal(19.0001).setScale(2, BigDecimal.RoundingMode.DOWN)

BigDecimal pi = new BigDecimal(3.14);
 BigDecimal pi4 = new BigDecimal(12.56);

 System.out.printf("%.2f",pi);

System.out.printf("%.0f",pi4);