Change a single parameter of Object in Hashmap

Question

I had to do a very basic "make a CAD project" for school and decided to make it a bit more challenging and add a way to interact more properly with the project. Basically, I have a Point class with a constructor that takes x and y coordinates as input and also has some methods.

Point(double x, double y) {
    this.x = x;
    this.y = y;
}

I wanted the user to be able to create as many points as he/she desires - and thus I went to Hashmaps (I tried lists too but I've read that Hashmaps are better for this, even though I couldn't find concrete answers to what I want in my project). The relevant snippet from my code looks as follows:

Map<Integer, Point> pMap = new HashMap<Integer, Point>();
double[] singlePoints = new double[2]; // temporarily store x and y coordinates
...
...
...
switch (intInput) {
    case 1:
        System.out.println("Create point? y/n");
        charInput = sc.next().charAt(0);
        if(java.lang.Character.toLowerCase(charInput) == 'y') {
            System.out.println("X coordinate: ");
            singlePoints[0] = sc.nextDouble();
            System.out.println("Y coordinate: ");
            singlePoints[1] = sc.nextDouble();
            pMap.put(pointCounter, new point(singlePoints[0], singlePoints[1]));
            pointCounter ++;
            break;
        } else {
            break;
        }
    case 2:
        System.out.println("Which point shall be edited?: ");
        int pointC2 = sc.nextInt();
        System.out.println("X or Y coordinate? ");
        char c2Input = java.lang.Character.toLowerCase(sc.next().charAt(0));
        if(c2Input == 'x') {
            ???
        }
}

The part with the question marks is where I want to change the x coordinate only. Since I haven't given the new Point (that is directly stored into the Hashmap ) a name, I can't access it with my getter and setter methods. How do I go on from here to change a single parameter (in this example it's 'x') of an object at a given index inside of the Hashmap ? If it's not possible, should I go back to normal Lists , and if so, how would I do that? (Also, a quick note: We haven't gotten to Lists or Hashmaps in the lectures as of now so my knowledge is based on what I found on the internet and doesn't come from experience or university)

Answer 1

As user input the desired point in pointC2 you might find the stored key in your map.

Point selectedPoint = pMap.get(pointC2);
selectedPoint.setX(newX);

// pMap.get(pointC2).setX(newX);

You did store a key in

pMap.put(pointCounter, new point(singlePoints[0], singlePoints[1]));

Your key is pointCounter