Pi approximation in Java

piapprox.java

public class PiApprox {
  public static void main(String[] args) {
    int precision = 16;

    double targetPi = roundTo(Math.PI / 4, precision);
    double pi = 0d;
    int i = 0;
    while (roundTo(pi, precision) != targetPi) {
      int sign = i % 2 == 0 ? 1 : -1;
      pi += 1d / (i++ * 2 + 1) * sign;
    }
    pi = roundTo(pi * 4, precision);

    System.out.println("Target: " + targetPi);
    System.out.println("Result: " + pi);
  }

  // Rounds number to a specific precision, i.e. roundTo(3.14159, 2) = 3.14)
  public static double roundTo(double number, int precision) {
    int exponent = (int) Math.pow(10, precision);
    return (double) Math.round(number * exponent) / exponent;
  }
}