How to convert decimal to fractions?

Question

What I need to convert decimal to fractions. It is easy to convert to 10\'s feet.

1.5 => 15/10

This can do via this code:

Answer 1

Given double x >= 0, int p, int q, find p/q as closest approximation:

• iterate on q from 1 upwards, determine p above and below; check deviations

So (not tested):

public static Rational toFraction(double x) {
    // Approximate x with p/q.
    final double eps = 0.000_001;
    int pfound = (int) Math.round(x);
    int qfound = 1;
    double errorfound = Math.abs(x - pfound);
    for (int q = 2; q < 100 && error > eps; ++q) {
        int p = (int) (x * q);
        for (int i = 0; i < 2; ++i) { // below and above x
            double error = Math.abs(x - ((double) p / q));
            if (error < errorfound) {
                pfound = p;
                qfound = q;
                errorfound = error;
            }
            ++p;
        }
    }
    return new Rational(pfound, qfound);
}

You could try it for Math.PI and E.