Java从for循环中找到最小值

Question

I was having some problem when trying to find the minimum distance and from the minimum distance, I then plot two circles onto the map.

                    double distance = 0;
                    double minDistance;
                    convertedHotSpotGeomList = RetrieveHotSpotAsyncTask.convertedHotSpotGeom;
                    for(int i = 0; i < convertedHotSpotGeomList.size(); i++){
                        LatLng point1 = new LatLng(convertedHotSpotGeomList.get(i).getY(), convertedHotSpotGeomList.get(i).getX());                                 
                        LatLng point2 = new LatLng(convertedHotSpotGeomList.get(++i).getY(), convertedHotSpotGeomList.get(++i).getX());
                        distance = calculateHotSpot(point1, point2);
                        Log.i("DIST", String.valueOf(distance));
                        minDistance = distance;
                        if(minDistance < distance){
                            minDistance = distance;
                            Log.i("MIN", String.valueOf(minDistance));
                             CircleOptions circleOptions = new CircleOptions()
                                .center(point1)
                                .radius(1000)
                                .fillColor(Color.argb(95, 178, 30, 37))
                                .strokeColor(Color.TRANSPARENT);

                                googleBasemap.addCircle(circleOptions);

                                CircleOptions circleOptions1= new CircleOptions()
                                .center(point2)
                                .radius(1000)
                                .fillColor(Color.argb(95, 88, 130, 37))
                                .strokeColor(Color.TRANSPARENT);

                                googleBasemap.addCircle(circleOptions1);

                        }
                    }

Currently I am getting 15, 3, 15, 14 as DIST but I could not get the minDist as it is not printed out. Any ideas?

Thanks in advance.

Answer 1

You probably want:

    distance = calculateHotSpot(point1, point2);
    ....
    if(distance < minDistance){  
        minDistance = distance;

and initialize minDistance to Double.MAX_VALUE : double minDistance = Double.MAX_VALUE

The original few lines does not make much sense, because minDistance < distance would never evaluates to true since you just set minDistance = distance;

    distance = calculateHotSpot(point1, point2);
    ....
    minDistance = distance;
    if(minDistance < distance){ // will never happen
        minDistance = distance;

Updated:

More complete solution as the point above is not the only issue:

double minDistance = Double.MAX_VALUE;
convertedHotSpotGeomList = RetrieveHotSpotAsyncTask.convertedHotSpotGeom;
LatLng[] minPoints = new LatLng[2]; // save the minimum points
for(int i = 0; i < convertedHotSpotGeomList.size(); i++){
    LatLng point1 = new LatLng(convertedHotSpotGeomList.get(i).getY(),   convertedHotSpotGeomList.get(i).getX());                                 
    LatLng point2 = new LatLng(convertedHotSpotGeomList.get(++i).getY(), convertedHotSpotGeomList.get(++i).getX());
    distance = calculateHotSpot(point1, point2);
    Log.i("DIST", String.valueOf(distance));
    if(distance < minDistance){
        minDistance = distance;
        Log.i("MIN", String.valueOf(minDistance));
        minPoints[0] = point1;
        minPoints[1] = point2;
    }
}
// we finish all the comparison, so we draw the circles now 
if(minPoints[0]!=null && minPoints[1] !=null){
    CircleOptions circleOptions = new CircleOptions()
        .center(minPoints[0])
        .radius(1000)
        .fillColor(Color.argb(95, 178, 30, 37))
        .strokeColor(Color.TRANSPARENT);
    CircleOptions circleOptions1= new CircleOptions()
        .center(minPoints[1])
        .radius(1000)
        .fillColor(Color.argb(95, 88, 130, 37))
        .strokeColor(Color.TRANSPARENT);

    googleBasemap.addCircle(circleOptions);
    googleBasemap.addCircle(circleOptions1);
}

Answer 2

Your problem lies in these two lines next to each other:

                    minDistance = distance;
                    if(minDistance < distance){

So first you are setting minDistance to the value of distance. Then you are checking to see if minDistance is less than distance. Since it will never be less than the value you just set it to, that block of code will never evaluate.