Using null for super parameter
<p>If an abstract superclass has a constructor which only defines initial field parameters, and one of the subclasses does not use one of the field parameters in its initialization, can I simply put a "null" where the unused field argument goes in the super() call? </p>

<p>To illustrate this more clearly, here's an example: </p>

<pre><code>public abstract class SuperClass {
    protected int xPos;
    protected int yPos;
    protected int zPos; 

    public SuperClass(int xPos, int yPos, int zPos) {
        this.xPos = xPos;
        this.yPos = yPos;
        this.zPos = zPos;
    }
    ... getters &amp; setters, etc.
}

public class SubClass extends SuperClass {
    public SubClass(int xPos, int yPos) {
        super(xPos, yPos, null);
    }
}
</code></pre>

<p>Is this acceptable? Is this good coding practice? Or is it better to have multiple constructors to accept the different types of arguments? </p>
