How to get the exponent of a double in a power of 10 in java?

Question

(Sorry I don't know what is the best keyword to describe this problem.)

The main problem is, if I have a double number in java, say 25.003, how can I know that this number can be written in 25003 x 10^(-3), so that I can get the exponent part (-3)?

The only thing I desire is to get that exponent number (-3). (so I know I can multiply 25.003 by 1000 to make it an integer) Is there any method gives me that exponent number?

Thanks a lot.

Answer 1

This is actually pretty simple if you think of it as a String.

private static int getExponentForNumber(double number)
{
    String numberAsString = String.valueOf(number);
    return numberAsString.substring(numberAsString.indexOf('.') + 1).length() * -1;
}

This is just returning the length after the "." which is your negative exponent. So you can really just use it like that:

int exponent = getExponentForNumber(25.003);
int basis = Integer.valueOf(String.valueOf(25.003).replace(".", ""));
String expression = "25.003 equals " + basis + "*10^" + exponent;
System.out.println(expression);

25.003 equals 25003*10^-3