Incorrect calculation result

[Sunny Jaiswal]

Here is a samll program that calculates (3 + sqroot(5))^22, but the result is wrong!!!

  
public class Test {
public static void main(String [] args) {
// Calculate sq root of 5 and add 3 and then power by 22.
double value = Math.pow((3 + Math.sqrt(5)), 22);
System.out.printf("value = %f", value);
// Should be                   6578336356630527.9973257393525212 (using windows calculator)
// But it prints value = 6578336356630531.000000
}
}  

Can someone please tell me what is the problem in the code, thanks in advance.

[Ulf Dittmer]

Using a "double" will give you only about 14 significant digits. Seeing that both results are identical in the first 14 digits, that's as good as it's going to get. See #20 in the http://faq.javaranch.com/java/JavaBeginnersFaq for some background of why this is so.

For more precision, use the BigDecimal class. Various implementations of the square root for BigDecimal are available on the net.
[ July 26, 2008: Message edited by: Ulf Dittmer ]

[Sunny Jaiswal]

Wow, that's a lot of information, thanks...