How to create a multipart polyline

static IPolyline constructMultiPartPolyline(IPolyline inputPolyline)throws Exception{
    IGeometry outGeometry = new Polyline();

    //Always associate new, top-level geometries with an appropriate spatial reference.
    outGeometry.setSpatialReferenceByRef(inputPolyline.getSpatialReference());

    IGeometryCollection geometryCollection = (IGeometryCollection)outGeometry;

    ISegmentCollection segmentCollection = (ISegmentCollection)inputPolyline;

    //Iterate over existing polyline segments using a segment enumerator.
    IEnumSegment segments = segmentCollection.getEnumSegments();

    ISegment[] currentSegment = new ISegment[1];
    int[] partIndex = new int[1];
    int[] segmentIndex = new int[1];
    segments.next(currentSegment, partIndex, segmentIndex);
    while (currentSegment != null){
        ILine normal = new Line();

        //Geometry methods with _Query_ in their name expect to modify existing geometries. 
        //In this case, the QueryNormal method modifies an existing line
        //segment (normal) to be the normal vector to 
        //currentSegment at the specified location along currentSegment.
        currentSegment[0].queryNormal(esriSegmentExtension.esriNoExtension, 0.5,
            true, currentSegment[0].getLength() / 3, normal);

        //Since each normal vector is not connected to others, create a new path for each one.
        ISegmentCollection newPath = new Path();
        newPath.addSegment((ISegment)normal, null, null);
        //The spatial reference associated with geometryCollection will be assigned to all incoming paths and segments.
        geometryCollection.addGeometry((IGeometry)newPath, null, null);

        segments.next(currentSegment, partIndex, segmentIndex);
    }
    //The geometryCollection now contains the new, multipart polyline.
    return (IPolyline)geometryCollection;
}