public class Ring {
    Ring left;
    Ring right;
    Object value;

    Ring(Object value) {
        this.value = value;
        left = this;
        right = this;
    }
    public Object value() { return value; }

    public Ring left() { return left; }

    public Ring right() { return right; }

    public String toString() {
        Ring r = this;
        String ans = "Ring[";
        do {
            if (r != this) ans = ans + ", ";
            ans = ans + r.value.toString();
            r = r.right;
        } while (r != this);
        return ans + "]";
    }
    public void join(Ring r) {
        r.left.right = right;
        right.left = r.left;
        r.left = this;
        right = r;
    }
    public void insert(Object value) {
        join(new Ring(value));
    }
    public static class Exception extends java.lang.Exception {}

    public static Ring fromArray(Object[] array) throws Ring.Exception {
        if (array.length == 0) throw new Ring.Exception();
        Ring r = new Ring(array[0]);
        for (int i = array.length-1; i > 0; i--) {
            r.insert(array[i]);
        }
        return r;
    }
    public static void main(String[] args)
            throws java.io.IOException, Ring.Exception {
        String[] abc = {"a", "b", "c"};
        Ring a = fromArray(abc);
        System.out.println(a); // Ring[a, b, c]
        Ring d = new Ring("d");
        Ring f = new Ring("f");
        d.join(f);
        d.insert("e");
        System.out.println(d); // Ring[d, e, f]
        a.join(d);
        System.out.println(a); // Ring[a, d, e, f, b, c]
        System.out.println(d); // Ring[d, e, f, b, c, a]
        a.join(f);
        System.out.println(a); // Ring[a, f, b, c]
        System.out.println(d); // Ring[d, e]
        System.in.read();
    }
}