Java – LinkedList class

LinkedList:

• LinkedList maintains insertion order of elements as it is implementing Queue interface.
• If we create object for LinkedList and with LinkedList reference variable, we can access complete functionality of Queue, List and Deque.

import java.util.*;
class LinkedListDemo 
{
	public static void main(String[] args) 
	{
		LinkedList list = new LinkedList();
		
		list.add(100);
		list.add(200);
		System.out.println("List : "+list);

		list.addFirst(111);
		list.addLast(222);
		System.out.println("List : "+list);

		System.out.println("Peek : "+list.peek()); //Returns top element but not remove
		System.out.println("After peek List : "+list);

		System.out.println("Poll : "+list.poll()); //Returns top element & remove
		System.out.println("After poll List : "+list);
	}
}

Note : If we collect LinkedList object address into a particular implemented interface type, we cannot access all the interfaces functionality.

import java.util.*;
class LinkedListDemo 
{
	public static void main(String[] args) 
	{
		Queue q = new LinkedList();
		q.add(100);
		q.add(200);
		System.out.println("Queue : "+q);
		System.out.println("Peek : "+q.peek()); 

		q.addFirst(111); // Error : not specified in Queue
		System.out.println("Queue : "+q);
	}
}

Output this following code:

import java.util.*;
class LinkedListDemo{
	public static void main(String[] args) {
		LinkedList l = new LinkedList();
		for(int i=10 ; i<=100 ; i+=10){
			l.add(new Integer(i));
		}
		System.out.println("List : "+l);			
		for(int i=0 ; i<l.size() ; i++){
			System.out.println("Poll : "+l.poll());
		}
	}
}