Converting code from using doubles to BigDecimal

Question

I've been writing a CAD type program for fun in JAVA. The other day I wrote some code to define a line which was tangent to 2 circles. I've been checking my numbers with a commercial CAD program and they have been fairly close. Usually to the 9th decimal point. My results really only need to be stored in an array to 7 decimal points. After successfully defining the line tangent to the 2 circles, I decided to test it and define a point which was the intersection of the line and one of the circles. In one case I got the result I was looking for, in another case I got no intersection. After looking at a few of the calculations I realized I was getting a very very small variation of maybe 9 or ten decimal places. I'm thinking of rewriting the code using BigDecimal.

This is a small snippet of some of the code I need to rewrite. Once I started it became much more cumbersome than I was wanting to do. I'm thinking about just converting the results using BigDecimal and using the original code unless there is an easy way to convert the following code to a BigDecimal type of format.

    private float[] offsetLine(float lnx1, float lny1, float lnz1, float lnx2, float lny2, float lnz2, String direction, float offset) {
        
        
        double deltax = Math.abs(lnx2 - lnx1);
        double deltay = Math.abs(lny2 - lny1);
        double lineLength = Math.sqrt(deltax * deltax + deltay * deltay);
        
        double stepx = (offset * deltay) / lineLength;
        double stepy = (offset * deltax) / lineLength;
        
        
    

Answer 1

Ok I'll answer my own question. Here's some code I dug up. I could only round to 6 decimal places to get the rounding I wanted. Once I did my calculations in double values I called the subroutine roundDbl

double checkRadius1 = Math.sqrt(((cir1x - offsetpts[0])*(cir1x - offsetpts[0])) + ((cir1y - offsetpts[1]) * (cir1y - offsetpts[1])));

double checkRadiusRounded = roundDbl(checkRadius1, 6); //round to 6 decimal places

public static Float roundDbl(Double dblValue, int decimalPlace) {

        String tempDblString = Double.toString(dblValue);

        String tempDbl = new BigDecimal(tempDblString).setScale(decimalPlace, RoundingMode.HALF_UP).stripTrailingZeros().toPlainString();
        
        return Float.valueOf(tempDbl);
    }