public class SingLList {

    private Node head;

    private static class Node {
        public int data;
        public Node next;
    }

    public static void main(String[] args) {
        int[] arr = {1,2,3,4,5,6,7};
        SingLList list = SingLList.arrayToList(arr);
        list.showList();
        System.out.println();
        list.addBack(8);
//        list.removeOdd();
//        list.showList();
//        list.addFront(1);
//        System.out.println();

        list.showList();
//        System.out.println("contains 3? "+list.contains(3));
//        System.out.println("contains 8? "+list.contains(8));
//        list.clear();
//        list.showList();
    }

    public boolean empty() {
        return this.head == null;
    }

    public void addFront(int d) {
            if ( this.head.data == 0) {
                this.head.data = d;
                this.head.next = null;
            }
            else {
                SingLList list = new SingLList();
                list.head = new Node();
                list.head.data = d;
                list.head.next = this.head;
                this.head = list.head;
            }
    }
    public void addBack(int d) {
        if( this.empty() ) {
            this.head = new Node();
            this.head.data = d;
            System.out.print("*");
        }
        else {
            SingLList list = new SingLList();
            list.head = this.head.next;
            list.addBack(d);

        }
    }
    public static SingLList arrayToList(int[] arr) {
        SingLList list = new SingLList();
        list.head = new Node();
        for ( int i = arr.length; i > 0; i-- ) {
            list.addFront(arr[i-1]);
        }
        return list;
    }
    public void removeOdd() {
        SingLList list = new SingLList();
        list.head= new Node();
        while(! this.empty()) {
            if ( this.head.data % 2 == 0) {
                list.addFront(this.head.data);
            }
            this.head = this.head.next;
        }

        this.head = list.head;
    }
//    public boolean contains(int d)
    public void showList() {
        SingLList temp = new SingLList();
        System.out.print(this.head.data+" ");
       if ( this.head.next != null ) {
           temp.head = this.head.next;
           temp.showList();
       }
    }
    //public void clear()

}