How to get first non-zero digit of a BigDecimal

Question

In java how do I get the first non-zero digit of a BigDecimal?

For example:

0.001 => 1
0.02 => 2
987.654 => 9

For numbers between 0 and 1 this will work:

bigDecimal.scaleByPowerOfTen(bigDecimal.precision()).setScale(0, RoundingMode.DOWN)

For numbers bigger than 1 this will work:

bigDecimal.scaleByPowerOfTen(1-bigDecimal.precision()).setScale(0, RoundingMode.DOWN)

But is there a solution, that works for any number?

Answer 1

Here's a solution using just BigDecimal and int:

BigDecimal value = new BigDecimal(0.021); //input your value here

int scale = value.scale();
int precision = value.precision();
int result = value.movePointLeft(precision-scale-1).abs().intValue(); //this will generate the result you need