public class DoubleNode<C> {
    private C data;
    private DoubleNode<C> next,prev;
    public DoubleNode(C the_data){
        data=the_data;
        next=null;
        prev=null;
    }

    public C getData(){
        return data;
    }
    public void setNext(DoubleNode<C> theNext){
        next=theNext;
    }
    public DoubleNode<C> getNext(){
        return next;
    }

    public void setPrev(DoubleNode<C> thePrev){
        prev=thePrev;
    }
    public DoubleNode<C> getPrev(){
        return prev;
    }

    public void print(){
        System.out.println(this.toString());
    }

    public String toString() {
        return "[" + data.toString() + ";" + formatRef(prev) + ";" + formatRef(next) + "]";
    }

    private static <T>String formatRef(DoubleNode<T> ref) {
        if (ref == null)
            return "null";
        else
            return "<" + ref.data.toString() + ">";
    }
    public static void main(String [] args) {
        DoubleNode<String> node=new DoubleNode<>("foo");
        DoubleNode<String> other=new DoubleNode<>("bar");
        node.setNext(other);
        other.setPrev(node);
        System.out.println(node.toString());
    }
}