Method insert

LabEnv/05Lab/PointSET.java:34–37

(Point2D p)

    // add the point to the set (if it is not already in the set)
    public void insert(Point2D p) {
        if (p == null) throw new IllegalArgumentException();
        treeSet.add(p);
    }

    // does the set contain point p?
    public boolean contains(Point2D p) {