New to Java

Hi, I'm a beginner in using Hashmap and there is something that is turning me crazy but should be very easy if I had the concepts clear.
I'm trying to use a HashMap to store some float (energy) values for each point in space represented by a coordinate(x,y,z) defined in a simple class that I call Coord3d.
I have apparently no problem in creating the hashmap and filling it up with the energy values for each coordinate.

My problem comes when I try to read the value for any given coordinate:
1.- If I use something like
coord= new Coord3d((float) 0.0, (float) 0.0, (float) 0.0);
energy= energyValues.get(coord);
I get a NullPointer exception in the "get"

2.- If I assign values directly as in:
coord.x= (float) 0.0;
coord.y= (float) 0.0;
coord.z= (float) 0.0;
energy= energyValues.get(coord);

The "get" function of the Hasmap does not return the energy value of the searched coordinate but instead it returns the last stored value.

Attached I send a very simple and short testcase that reproduces my problems.
Thanks for any help and best regards,

JBB

import java.util.HashMap;
public class testCaseHashMap {
	public static void main(String[] args) {
		HashMap<Coord3d, Float> energyValues;
		energyValues = new HashMap<Coord3d, Float>(); //Must use Object Float instead of primitive data type float 
		Coord3d coord= new Coord3d(-20.0f, -20.0f, -20.0f);
		float energy=0.0f;
		float x = 0,y = 0,z = 0;
		
		for(int incX=0; incX<2; incX++){
			for(int incY=0; incY<2; incY++){
				for(int incZ=0; incZ<2; incZ++){
					x= (float) incX;
					y= (float) incY;
					z= (float) incZ;
					energy= (float) x+y+z;
					coord= new Coord3d(x, y, z);
					energyValues.put(coord,energy);
					System.out.println("x= "+String.valueOf(x)+" y= "+String.valueOf(y)+" z= "+String.valueOf(z)+" "+String.valueOf(energy));
				}
			}
		}	
 // If I use new I get a NullPointerException
		coord= new Coord3d((float) 0.0, (float) 0.0, (float) 0.0); 

//If instead I set manually the values it doesn't produce an error but gets the last value instead of the one with matching key
		coord.x= (float) 0.0; 
		coord.y= (float) 0.0;
		coord.z= (float) 0.0;

		energy= energyValues.get(coord);
		System.out.println(String.valueOf(energy));
	}
}

And the simple definition of the Coord3d class:

public class Coord3d {		
	/** Create a 3d coordinate.*/
	public Coord3d(float xi, float yi, float zi){
		x = xi;
		y = yi;
		z = zi;
	}
	
	public float x;
	public float y;
	public float z;
}