如何从hashMap查找所有第一个值

Question

I have a list with HashMap<Integer, Point3d> format like in the following way.

 {
   {key1,(x1,y1,z1)},
   {key2,(x2,y2,z2)},
   {key3,(x1,y3,z3)},
   {key4,(x1,y4,z4)},
   {key5,(x5,y5,z5)},
   ..
 }

First I want to seperate first elements from all the points like {x1,x2,x1,x1,x5} and then remove duplicates like {x1,x2,x5} finally length of the result means {x1,x2,x5}.size()

In the same way I want to implement for 2nd and 3rd elements of the Points .

I tried allot but I didn't find anyway.because we can't able to retrieve values from HashMap based on index . we can able to retrieve values based on Key value But I don't know the Keyvalues hashMap.

I tried in the following way.

  public int xSideLength(HashMap<Integer, Point3d> coOrdinates) {
    int length=0;
    Set<Integer> keyValues=coOrdinates.keySet();
    Integer[] array=(Integer[]) keyValues.toArray();
    for (int index = 0; index < array.length; index++) {
        //logical code
    }
    return length;
}

Can anyone suggest me.

Answer 1

What do you think of the following:

Set<Integer> values = new HashSet<Integer>();
for(Point3d point : coordinates.values()) {
    values.add(point.x());
}

return values.size();

Answer 2

You can follow the following steps,

1. Put the values of the HashMap into a Set with your custom Comparator .
2. Implement your compare method.
3. Return the set size.

The snippet looks like below,

public int xSideLength(HashMap<Integer, Point3d> coOrdinates) {
    int length=0;
    Set<Point3d> values = new TreeSet<Point>(new Comparator<Point3d>() {
        @Override
        public int compare(Point3d e1, Point3d e2) {
            return e1.getX().compareTo(e2.getX());
        }
    });
    values.addAll(coOrdinates.values());
    return values.size();
}

Answer 3

You can get elements from the map using the key like this:

Set<Integer> keyValues = coOrdinates.keySet();
for (Integer key : keyValues) {
    Point3d point = coOrdinates.get(key);   
    // Your logical code goes here.
}

Answer 4

public static void zz() {
    Map<String,Point3d> m = new HashMap<String,Point3d>();

    m.put("k1", new Point3d(1.0, 1.0, 4.0));
    m.put("k2", new Point3d(2.0, 2.0, 2.0));
    m.put("k3", new Point3d(1.0, 3.0, 2.0));
    m.put("k4", new Point3d(1.0, 3.0, 4.0));
    m.put("k5", new Point3d(5.0, 3.0, 2.0));

    Set xvals = new HashSet();
    Set yvals = new HashSet();
    Set zvals = new HashSet();

    double[] coords = new double[3];
    for (Point3d p : m.values()) {
        p.get(coords);
        xvals.add(coords[0]);
        yvals.add(coords[1]);
        zvals.add(coords[2]);
    }

    System.out.println("# unique x: " + xvals.size() + ": " + xvals);
    System.out.println("# unique y: " + yvals.size() + ": " + yvals);
    System.out.println("# unique z: " + zvals.size() + ": " + zvals);
    }

Answer 5

for (Map.Entry<Integer, Point3d> entry : coOrdinates.entrySet()) {
    Point3d point = entry.getValue());
}