dap4/d4cdm/src/main/java/dap4/cdm/nc2/CDMArrayStructure.java
@Override
    public StructureData
    getStructureData(int index)
    {
        assert (super.sdata != null);
        if(index < 0 || index >= this.dimsize)
            throw new IllegalArgumentException(index + " >= " + super.sdata.length);
        assert (super.sdata[index] != null);
        return super.sdata[index];
    }
@Override
    public StructureData
    getStructureData(int index)
    {
        assert (super.sdata != null);
        if(index < 0 || index >= this.dimsize)
            throw new IllegalArgumentException(index + " >= " + super.sdata.length);
        assert (super.sdata[index] != null);
        return super.sdata[index];
    }
Get the index'th StructureData(StructureDataA) object
We need instances of StructureData to give to the user.
We use StructureDataA so we can centralize everything
in this class. The total number of StructureData objects
is dimsize.

@param index
@return