OldCheckpoints.java

import java.util.ArrayList;
import java.util.List;

public class OldCheckpoints {
	
	private boolean completed = false;
	
	private List<Point> chechpoints = new ArrayList<>();
	
	private Point first;
	
	private Point current;

	public boolean isCompleted() {
		return completed;
	}

	public void setCurrent(Point p) {
		if (p.equals(current)) {
			return;
		}
		current = p;
		if (completed) {
			return;
		}
		if (current.equals(first)) {
			completed = true;
			return;
		}
		if (first == null) {
			first = current;
		}
		chechpoints.add(p);
		
	}

	public Point  nextCheckpoint() {
		return nextCheckpoint(current);
	}

	public Point nextCheckpoint(Point currentCheckpoint) {
		if (!completed) {
			throw new IllegalStateException("Dude, not completed yet. Call isCompleted() next time");
		}
		int idx = chechpoints.indexOf(currentCheckpoint);
		if (idx == -1) {
			throw new IllegalStateException("Dude, uknown " + currentCheckpoint);
		}
		int nextIdx =  (idx + 1) % chechpoints.size();
		return chechpoints.get(nextIdx);
	}


}