Java Math.

Math

• Math.round()

BigDecimal

   java.math.BigDecimal

• BigDecimal (int)
• BigDecimal (double)
• BigDecimal (long)
• BigDecimal (String) // better

• Methods
• add (value)
• compareTo(value)
• divide(value, scale, rounding-mode)
• multiply(value)
• setScale(scale, rounding-mode)
• subtract(value)
• toString()

   java.math.RoundingMode

• HALF_UP
• HALF_EVEN

import java.math.*; // imports all classes and 
                    // enumerations in java.math

// convert subtotal and discount percent to 
BigDecimal BigDecimal decimalSubtotal =
    new BigDecimal(Double.toString(subtotal)); 
decimalSubtotal =
    decimalSubtotal.setScale(2, RoundingMode.HALF_UP); 
BigDecimal decimalDiscountPercent =
    new BigDecimal(Double.toString(discountPercent));

// calculate discount amount 
BigDecimal discountAmount =
    decimalSubtotal.multiply(decimalDiscountPercent); 
discountAmount = discountAmount.setScale(
    2, RoundingMode.HALF_UP);
// calculate total before tax, sales tax, and total
BigDecimal totalBeforeTax =
   decimalSubtotal.subtract(discountAmount);
BigDecimal salesTaxPercent =
   new BigDecimal(SALES_TAX_PCT);
BigDecimal salesTax =
   salesTaxPercent.multiply(totalBeforeTax);
salesTax = salesTax.setScale(2, RoundingMode.HALF_UP);
BigDecimal total = totalBeforeTax.add(salesTax);

// Create another BigDecimal object from existing BigDecimal Object
BigDecimal total2 = new BigDecimal(total.toString());