LinkedList class

In this chapter you will learn:

LinkedList class

LinkedList class

The LinkedList class extends AbstractSequentialList and implements the List, Deque, and Queue interfaces. It provides a linked-list data structure. LinkedList is a generic class that has this declaration:

class LinkedList<E>

E specifies the type of objects that the list will hold.

A demonstration of a linked list of nodes

import java.util.LinkedList;
import java.util.List;
import java.util.ListIterator;
/*from  j av  a 2  s  . c  o m*/
public class Main {
  public static void main(String[] args) {
    List<String> ls = new LinkedList<String>();
    String[] weekDays = { "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" };
    for (String weekDay : weekDays){
      ls.add(weekDay);
    }      
    dump("ls:", ls);
    ls.add(1, "A");
    ls.add(3, "B");
    ls.add(5, "C");
    dump("ls:", ls);
    ListIterator<String> li = ls.listIterator(ls.size());
    while (li.hasPrevious()){
      System.out.print(li.previous() + " ");
    } 
  }

  static void dump(String title, List<String> ls) {
    System.out.print(title + " ");
    for (String s : ls){
      System.out.print(s + " ");
    }      
    System.out.println();
  }
}

Because LinkedList implements the Deque interface, you have access to the methods defined by Deque.

For example,

To add elements to the start of a list you can use addFirst( ) or offerFirst( ).
To add elements to the end of the list, use addLast( ) or offerLast( ).
To obtain the first element, you can use getFirst( ) or peekFirst( ).
To obtain the last element, use getLast( ) or peekLast( ).
To remove the first element, use removeFirst( ) or pollFirst( ).
To remove the last element, use removeLast( ) or pollLast( ).