Ideal Gas Calculation

public class idealGas {

// derives all equations from:
// (atmospheres) * (liters) = ((mass) / (molar mass)) * (R [constant equal to 0.082057]) * (kelvin) 

private double pressure;                        // in atm
private double volume;                          // in L
private double mass;                            // in g
private double molarMass;                       // in g mol^-1
private final double R = 0.082057;              // in L atm mol^-1 K^-1
private double temperature;                     // in K

// new ideal gas
public idealGas() {
    pressure = 1;
    volume = 22.4;
    mass = 12;
    molarMass = 12;
    temperature = 273.15;
}

// resets to default
public void resetGas() {
    idealGas()

// returns pressure
public double pressure() {
    return pressure;
}

// returns volume
public double volume() {
    return volume;
}

// returns mass
public double mass() {
    return mass;
}

// returns molar mass
public double molarMass() {
     return molarMass;
}

// returns moles
public double moles() {
    return mass / molarMass;
}

// returns temperature
public double temperature() {
    return temperature;
}

// sets pressure to x
public void setPressure(double x) {
    pressure = x;
}

// sets volume to x
public void setVolume(double x) {
    volume = x;
}

// sets mass to x
public void setMass(double x) {
    mass = x;
}

// sets molar mass to x
public void setMolarMass(double x) {
    molarMass = x;
}

// sets moles to x
public void setMoles(double x) {
    mass *= x;
}

// set temperature to x
public void setTemperature(double x) {
    temperature = x;
}

// calculates for pressure
public double calculatePressure() {
    pressure = ((mass / molarMass) * R * temperature) / volume;
    return pressure;
}

// calculates for volume
public double calculateVolume() {
    volume = ((mass / molarMass) * R * temperature) / pressure;
    return volume;
}

// calculates for mass
public double calculateMass() {
    mass = ((pressure * volume) / (R * temperature)) * molarMass;
    return mass;
}

// calculates for molar mass
public double calculateMolarMass() {
    molarMass = mass / ((pressure * volume) / (R * temperature));
    return molarMass;
}

// calculates for moles
public double calculateMoles() {
    return ((pressure * volume) / (R * temperature));
}

// calculates for temperature
public double calculateTemperature() {
    temperature = (pressure * volume) / ((mass / molarMass) * R);
    return temperature;
}

// converts to string
public String toString() {
    return "Pressure: " + pressure + "\n" +
           "Volume: " + volume + "\n" +
           "Mass: " + mass + "\n" +
           "Molar Mass: " + molarMass + "\n" +
           "Moles: " + (mass / molarMass) + "\n" +
           "Temperature: " + temperature;
}

// compares for equality
public boolean equals(Object o) {
    if( o instanceof idealGas) {
        O = (idealGas) o;
        if(O.pressure() == pressure &&
           O.volume() == volume &&
           O.mass() == mass &&
           O.molarMas() == molarMass &&
           O.temperature() == temperature) {
            return true;
        } else {
            return false;
        }
    } else {
        return false;
    }
}

}