LinkedList
1) Introduced in 1.2 v
2) Duplicate objects are allowed
3) Null insertion is possible
4) Heterogeneous objects are allowed
5) The under laying data structure is double linked list.
6) Insertion ode is preserved.
LinkedList class methods:
void addFirst(int i, obj) :
This method adds the element obj at the first position of the linked list. 

void addLast(int i, obj) :
This method appends the specified element to the end of list.

element removeLast() :
This method removes the last element from the list and returns it. 

element remove(int i) :
This removes an element at the specified position i in the linked list.

element getFirst() :
This method returns the first element from the list. 

element getLast() :
This method returns the last element from the list.
LinkedList with generics
import java.util.*; 
class Test
{ 
public static void main(String[] args) 
{ 
LinkedList l=new LinkedList(); 
l.add("a"); 
l.add("ratan"); 
l.add("anu"); 
l.add("aaa"); 
System.out.println(l.size()); 
} 
}
Output :
4
LinkedList program
import java.util.ArrayList; 
import java.util.*; 
class Test 
{ 
public static void main(String[] args) 
{ 
LinkedList ll=new LinkedList(); 
System.out.println(ll.size()); 
//add the elements to the LinkedList 
ll.add("a"); 
ll.add(10); 
ll.add(10.6); 
ll.addFirst("ramana"); 
ll.addLast("anu"); 
System.out.println("original content :"+ll); 
System.out.println(ll.size()); 
//remove elements from LinkedList 
ll.remove(10.6); 
ll.remove(0); 
System.out.println("after deletion content :"+ll); 
System.out.println(ll.size()); 
//remove first and last elements 
ll.removeFirst(); 
ll.removeLast(); 
System.out.println("ll after deletion of first and last :"+ll); 
//get and set a value 
int a=(Integer)ll.get(0); 
ll.set(0,a+"ramana"); 
System.out.println("ll after change:"+ll); 
} 
}
Output :
0
original content :[ramana, a, 10, 10.6, anu]
5
after deletion content :[a, 10, anu]
3
ll after deletion of first and last :[10]
ll after change:[10ramana]