Bigdecimal

Lately, after publishing the previous post, a friend of mine passed me a snipped of BigDecimal code. He was wondering, why the following execution: BigDecimal a = new BigDecimal(2.9); BigDecimal b = new BigDecimal(4000); MathContext mc = new MathContext(2, RoundingMode.HALF_DOWN); BigDecimal r1 = a.multiply(b, mc); BigDecimal r2 = a.multiply(b).setScale(2, RoundingMode.HALF_DOWN); System.out.println("r1 = " + r1); System.out.println("r2 = " + r2); is returning different values for r1 and r2: r1 = 1....

There is a well known problem with precise floating point numbers representation in a computer, and Java is no different in this case. If you want to see it for yourself, than try executing the below code: Double d = new Double(4.395f); System.out.println(d); You might expect the 4.395 will be printed out, right? Well, you’re defining an “exact” number as a float (32 bit), than casting it to the double (64 bit) so there should be no problem, as it shouldn’t affect the value....