How to create new double number with 2 numbers before and 2 numbers after dot from a previous double number?

Question

I need help to create a new double number by selecting 2 numbers before dot and 2 numbers after dot from a previous double number.

For example:

Double number: 1054001.4032

New double number: 1.40

Double number: 2015.0634547

New double number: 15.06

Double number: 319.00056

New double number: 19.00

So far, I found instructions on splitting (which is not the case). My goal is to create a new double number as shown above.

Answer 1

Try using String.split:

class Main {
    private static final int MAX_DIST_FROM_DECMIMAL_POINT = 2;

    public static double extractDouble(double num) {
        // 0. Return early if num is zero.
        if (num == 0) {
            return 0;
        }
        // 1. Cast the double into a string.
        String numStr = String.valueOf(num);
        // 2. Split the string at the decimal point into the integer and decimal parts.
        String[] parts = numStr.split("\\.");
        String intPart = parts[0];
        String decPart = parts[1];
        // 3. Extract substrings around decimal point.
        String newIntPart = intPart.substring(intPart.length() - Math.min(intPart.length(), MAX_DIST_FROM_DECMIMAL_POINT));
        String newDecPart = decPart.substring(0, Math.min(decPart.length(), MAX_DIST_FROM_DECMIMAL_POINT));
        // 4. Comine the two strings into a double.
        return Double.parseDouble(newIntPart + "." + newDecPart);
    }

    public static void main(String[] args) {
        double n1 = 1054001.4032;
        System.out.printf("%f => %.2f%n", n1, extractDouble(n1));
        double n2 = 2015.0634547;
        System.out.printf("%f => %.2f%n", n2, extractDouble(n2));
        double n3 = 319.00056;
        System.out.printf("%f => %.2f%n", n3, extractDouble(n3));
        double n4 = 1.2;
        System.out.printf("%f => %.2f%n", n4, extractDouble(n4));
    }
}

Output:

1054001.403200 => 1.40
2015.063455 => 15.06
319.000560 => 19.00
1.200000 => 1.20