Double-Ended Lists: list with first and last references : Your LinkedList « Collections « Java Tutorial

1. Java Tutorial
2. Collections
3. Your LinkedList

class Link {
  public int iData;

  public Link next;

  public Link(int id) {
    iData = id;
  }

  public String toString() {
    return "{" + iData + "} ";
  }
}

class FirstLastList {
  private Link first;
  private Link last;

  public FirstLastList() {
    first = null;
    last = null;
  }

  public boolean isEmpty() {
    return first == null;
  }

  public void insertFirst(int dd) {
    Link newLink = new Link(dd);
    if (isEmpty())
      last = newLink;
    newLink.next = first;
    first = newLink;
  }

  public void insertLast(int dd) {
    Link newLink = new Link(dd);

    if (isEmpty())
      first = newLink;
    else
      last.next = newLink;
    last = newLink;
  }

  public int deleteFirst() {
    int temp = first.iData;
    if (first.next == null)
      last = null;
    first = first.next;
    return temp;
  }

  public String toString() {
    String str = "";
    Link current = first;
    while (current != null) {
      str += current.toString();
      current = current.next;
    }
    return str;
  }
}

public class MainClass {
  public static void main(String[] args) {
    FirstLastList theList = new FirstLastList();

    theList.insertFirst(22);
    theList.insertFirst(44);
    theList.insertFirst(66);

    theList.insertLast(11);
    theList.insertLast(33);
    theList.insertLast(55);

    System.out.println(theList);

    theList.deleteFirst();
    theList.deleteFirst();

    System.out.println(theList);
  }
}

{66} {44} {22} {11} {33} {55} 
{22} {11} {33} {55}