How can I measure distance and create a bounding box based on two latitude+longitude points in Java?

Here is a Java implementation of Haversine formula. I use this in a project to calculate distance in miles between lat/longs.

public static double distFrom(double lat1, double lng1, double lat2, double lng2) {
    double earthRadius = 3958.75; // miles (or 6371.0 kilometers)
    double dLat = Math.toRadians(lat2-lat1);
    double dLng = Math.toRadians(lng2-lng1);
    double sindLat = Math.sin(dLat / 2);
    double sindLng = Math.sin(dLng / 2);
    double a = Math.pow(sindLat, 2) + Math.pow(sindLng, 2)
            * Math.cos(Math.toRadians(lat1)) * Math.cos(Math.toRadians(lat2));
    double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
    double dist = earthRadius * c;

    return dist;
    }

We've had some success using OpenMap to plot a lot of positional data. There's a LatLonPoint class that has some basic functionality, including distance.

For a more accurate distance (0.5mm) you can also use the Vincenty approximation:

/**
 * Calculates geodetic distance between two points specified by latitude/longitude using Vincenty inverse formula
 * for ellipsoids
 * 
 * @param lat1
 *            first point latitude in decimal degrees
 * @param lon1
 *            first point longitude in decimal degrees
 * @param lat2
 *            second point latitude in decimal degrees
 * @param lon2
 *            second point longitude in decimal degrees
 * @returns distance in meters between points with 5.10<sup>-4</sup> precision
 * @see <a href="http://www.movable-type.co.uk/scripts/latlong-vincenty.html">Originally posted here</a>
 */
public static double distVincenty(double lat1, double lon1, double lat2, double lon2) {
    double a = 6378137, b = 6356752.314245, f = 1 / 298.257223563; // WGS-84 ellipsoid params
    double L = Math.toRadians(lon2 - lon1);
    double U1 = Math.atan((1 - f) * Math.tan(Math.toRadians(lat1)));
    double U2 = Math.atan((1 - f) * Math.tan(Math.toRadians(lat2)));
    double sinU1 = Math.sin(U1), cosU1 = Math.cos(U1);
    double sinU2 = Math.sin(U2), cosU2 = Math.cos(U2);

    double sinLambda, cosLambda, sinSigma, cosSigma, sigma, sinAlpha, cosSqAlpha, cos2SigmaM;
    double lambda = L, lambdaP, iterLimit = 100;
    do {
        sinLambda = Math.sin(lambda);
        cosLambda = Math.cos(lambda);
        sinSigma = Math.sqrt((cosU2 * sinLambda) * (cosU2 * sinLambda)
                + (cosU1 * sinU2 - sinU1 * cosU2 * cosLambda) * (cosU1 * sinU2 - sinU1 * cosU2 * cosLambda));
        if (sinSigma == 0)
            return 0; // co-incident points
        cosSigma = sinU1 * sinU2 + cosU1 * cosU2 * cosLambda;
        sigma = Math.atan2(sinSigma, cosSigma);
        sinAlpha = cosU1 * cosU2 * sinLambda / sinSigma;
        cosSqAlpha = 1 - sinAlpha * sinAlpha;
        cos2SigmaM = cosSigma - 2 * sinU1 * sinU2 / cosSqAlpha;
        if (Double.isNaN(cos2SigmaM))
            cos2SigmaM = 0; // equatorial line: cosSqAlpha=0 (§6)
        double C = f / 16 * cosSqAlpha * (4 + f * (4 - 3 * cosSqAlpha));
        lambdaP = lambda;
        lambda = L + (1 - C) * f * sinAlpha
                * (sigma + C * sinSigma * (cos2SigmaM + C * cosSigma * (-1 + 2 * cos2SigmaM * cos2SigmaM)));
    } while (Math.abs(lambda - lambdaP) > 1e-12 && --iterLimit > 0);

    if (iterLimit == 0)
        return Double.NaN; // formula failed to converge

    double uSq = cosSqAlpha * (a * a - b * b) / (b * b);
    double A = 1 + uSq / 16384 * (4096 + uSq * (-768 + uSq * (320 - 175 * uSq)));
    double B = uSq / 1024 * (256 + uSq * (-128 + uSq * (74 - 47 * uSq)));
    double deltaSigma = B
            * sinSigma
            * (cos2SigmaM + B
                    / 4
                    * (cosSigma * (-1 + 2 * cos2SigmaM * cos2SigmaM) - B / 6 * cos2SigmaM
                            * (-3 + 4 * sinSigma * sinSigma) * (-3 + 4 * cos2SigmaM * cos2SigmaM)));
    double dist = b * A * (sigma - deltaSigma);

    return dist;
}

This code was freely adapted from http://www.movable-type.co.uk/scripts/latlong-vincenty.html

Kotlin version of Haversine formula. Returned result in meters. Tested on https://www.vcalc.com/wiki/vCalc/Haversine+-+Distance

const val EARTH_RADIUS_IN_METERS = 6371007.177356707

fun distance(lat1: Double, lng1: Double, lat2: Double, lng2: Double): Double {
    val latDiff = Math.toRadians(abs(lat2 - lat1))
    val lngDiff = Math.toRadians(abs(lng2 - lng1))
    val a = sin(latDiff / 2) * sin(latDiff / 2) +
        cos(Math.toRadians(lat1)) * cos(Math.toRadians(lat2)) *
        sin(lngDiff / 2) * sin(lngDiff / 2)
    val c = 2 * atan2(sqrt(a), sqrt(1 - a))
    return EARTH_RADIUS_IN_METERS * c
}

For Android, there is a simple approach.

 public static float getDistanceInMeter(LatLng start, LatLng end) { 
    float[] results = new float[1];
    Location.distanceBetween(start.latitude, start.longitude, end.latitude, end.longitude, results);
    return results[0];

}

;

https://developer.android.com/reference/android/location/Location#distanceBetween(lat1,lng1,lat2,lng2,output[])