code: public void invert() {
  		final PT p = this.startingPoint;
  		this.startingPoint = this.endingPoint;
  		this.endingPoint = p;
  		final int middle = this.segmentList.size() / 2;
  		ST segment;
  		for (int i = 0, j = this.segmentList.size() - 1; i < middle; ++i, --j) {
  			segment = this.segmentList.get(i);
  			this.segmentList.set(i, this.segmentList.get(j));
  			this.segmentList.set(j, segment);
  		}
  	}
docs: Revert the order of the graph segment in this path.