How can I add a method to my 3D point class to calculate the distance between two points?

I've created a Point3d class which contains x, y, and z coordinates for a point. My next task is to create a method within my class (which I shall call "distanceTo") that calculates the distance between two points.

How do I go about creating the method distanceTo that calculates the distance between two points by taking in the x,y,z coordinates? I assume my answer will have something to do with sqrt((x1-x2)^2+(y1-y2)^2+(z1-z2)^2) but I do not know how I can write that in my method in my main class if my points are not defined until my second test point class

So far I only have two points, but I am looking for a more general answer (so that if I created three points, p1 p2 and p3, I could calculate the distance between p1 and p2 or the distance between p2 and p3 or the distance between p1 and p3.

My class:

package divingrightin;

public class Point3d {
    
    private double xCoord;
    private double yCoord;
    private double zCoord;
    
    
    public Point3d(double x, double y, double z){
        xCoord = x;
        yCoord = y;
        zCoord = z;
    }
    
    public Point3d(){
        this (0,0,0);
    }
    
    public double getxCoord() {
        return xCoord;
    }
    public void setxCoord(double xCoord) {
        this.xCoord = xCoord;
    }
    public double getyCoord() {
        return yCoord;
    }
    public void setyCoord(double yCoord) {
        this.yCoord = yCoord;
    }
    public double getzCoord() {
        return zCoord;
    }
    public void setzCoord(double zCoord) {
        this.zCoord = zCoord;
    }
    
//  public double distanceTo(double xCoord, double yCoord, double zCoord ){
//      
//  }
}

My class with the test points:

package divingrightin;

public class TestPoints {

    public static void main(String[] args) {
        
        Point3d firstPoint = new Point3d();
        
        firstPoint.setxCoord(2.2);
        firstPoint.setyCoord(1);
        firstPoint.setzCoord(5);
        
        Point3d secondPoint = new Point3d();
        
        secondPoint.setxCoord(3.5);
        secondPoint.setyCoord(22);
        secondPoint.setzCoord(20);

    }

}

As @Dude pointed out in the comments, you should write a method:

public double distanceTo(Point3d p) {
    return Math.sqrt(Math.pow(x - p.getxCoord(), 2) + Math.pow(y - p.getyCoord(), 2) + Math.pow(z - p.getzCoord(), 2));
}

Then if you want to get the distance between 2 points you just call:

myPoint.distanceTo(myOtherPoint);
//or if you want to get the distance to some x, y, z coords
myPoint.distanceTo(new Point3d(x,y,z);

You could even make the method static and give it 2 points to compare:

public static double getDistance(Point3d p1, Point3d p2) {
    return Math.sqrt(Math.pow(p1.getxCoord() - p2.getxCoord(), 2) + ...
}