[MathHelper] #math

MathHelper.java

public class MathHelper {

    public static double distance(double dx, double dy) {
        return Math.sqrt(dx * dx + dy * dy);
    }

    public static double distance(double x0, double y0, double x1, double y1) {
        double dx = x1 - x0;
        double dy = y1 - y0;
        return distance(dx, dy);
    }

    public static double average(double... numbers) {
        if (numbers.length == 0) {
            return Double.NaN;
        }
        double sum = 0;
        for (int i = 0; i < numbers.length; i++) {
            sum += numbers[i];
        }
        return sum / numbers.length;
    }

    public static double variance(double... numbers) {
        if (numbers.length == 0) {
            return Double.NaN;
        }
        double sum_1 = 0;
        double sum_2 = 0;
        double avr = 0;
        for (int i = 0; i < numbers.length; i++) {
            sum_1 += numbers[i] * numbers[i];
            sum_2 += numbers[i];
        }
        avr = sum_2 / numbers.length;
        return (sum_1 + numbers.length * avr * avr + 2 * avr * sum_2) / numbers.length;
    }

    public static int gcd(int x, int y) {
        int max = Math.abs(Math.max(x, y));
        int min = Math.abs(Math.min(x, y));
        int r = max % min;
        if (r == 0) {
            return min;
        } else {
            while (r != 0) {
                max = min;
                min = r;
                r = max % min;
            }
            return min;
        }
    }

    public static int lcm(int x, int y) {
        int gcd = gcd(x, y);
        return x * y / gcd;
    }

    public static int pixel(float f) {
        if (f < 0f)
            return (int) (f - 0.5f);
        if (f > 0f)
            return (int) (f + 0.5f);
        return 0;
    }

    public static int pixel(double d) {
        if (d < 0d)
            return (int) (d - 0.5d);
        if (d > 0d)
            return (int) (d + 0.5d);
        return 0;
    }

    public static boolean tryParseBoolean(String string, boolean defaultValue) {
        try {
            return Boolean.parseBoolean(string);
        } catch (Exception e) {
            return defaultValue;
        }
    }

    public static byte tryParseByte(String string, byte defaultValue) {
        try {
            return Byte.parseByte(string);
        } catch (Exception e) {
            return defaultValue;
        }
    }

    public static int tryParseInt(String string, int defaultValue) {
        try {
            return Integer.parseInt(string);
        } catch (Exception e) {
            return defaultValue;
        }
    }

    public static long tryParseLong(String string, long defaultValue) {
        try {
            return Long.parseLong(string);
        } catch (Exception e) {
            return defaultValue;
        }
    }

    public static float tryParseFloat(String string, float defaultValue) {
        try {
            return Float.parseFloat(string);
        } catch (Exception e) {
            return defaultValue;
        }
    }

    public static double tryParseDouble(String string, double defaultValue) {
        try {
            return Double.parseDouble(string);
        } catch (Exception e) {
            return defaultValue;
        }
    }

}