Dealing with units and constants in physics

Acceleration.java

class Acceleration {

    public double metersPerSecondSquared;

    public double kilometersPerSecondSquared;

    public double newtonsPerKilogram;

    public Acceleration(double metersPerSecondSquared) {
        this.metersPerSecondSquared = metersPerSecondSquared;
        this.kilometersPerSecondSquared = metersPerSecondSquared / 1000;
        this.newtonsPerKilogram = metersPerSecondSquared;
    }


    public static void main(String[] args) {
        
        Acceleration accelerationEarth = new Acceleration(9.8);

        double timeSeconds = 10.0;
        double distanceMeters = accelerationEarth.metersPerSecondSquared * timeSeconds * timeSeconds;

    }
}

GravityConstants.java

public class GravityConstants {
    
    public static final Acceleration EARTH = new Acceleration(9.8);

    public static final Acceleration MOON = new Acceleration(1.6);

    public static final Acceleration SUN = new Acceleration(275);

    public static void main(String[] args) {
    

        // F = m g
        double massBallKilogram = 1.0;
        var earthGravityNewtons = massBallKilogram * GravityConstants.EARTH.newtonsPerKilogram;
    }
}

IdealGasConstant.java

public class IdealGasConstant {
    
    public double litersAtmospherePerKelvinPerMole; // L⋅atm⋅K−1⋅mol−1

    public double metersCubedPascalPerKelvinPerMole;	//m3⋅Pa⋅K−1⋅mol−1

    private static IdealGasConstant _instance = new IdealGasConstant();

    private IdealGasConstant() {
        this.litersAtmospherePerKelvinPerMole = 0.082057366080960;
        this.metersCubedPascalPerKelvinPerMole = 8.31446261815324;
    }

    public static IdealGasConstant getInstance() {
        return _instance;
    }

    public static void main(String[] args) {
        IdealGasConstant idealGasConstant = IdealGasConstant.getInstance();

        // P V = n R T

        double numberOfParticlesMole = 1;
        double temperatureKelvin = 273;
        double pressurePascal = 100;
        double volumeMetersCubed = numberOfParticlesMole * idealGasConstant.metersCubedPascalPerKelvinPerMole * temperatureKelvin / pressurePascal;
    }

}