LinkedList Java
LinkedList Java
- Java LinkedList class uses doubly linked list to store the elements.
- It provides a linked-list data structure.
- It inherits AbstractList class and implements List and Deque.
- LinkedList is better for manipulating elements whereas and ArrayList is best fit for storing and retrieving the data.
Linked List Types
- Non generic form of LinkedList
- Generic form of LinkedList
Non generic form of LinkedList
Syntax:
LinkedList object = new LinkedList();
Generic form of LinkedList
Syntax:
LinkedList<DataType> object = new LinkedList<DataType>();
Example:
package Mypkg;
import java.util.Iterator;
import java.util.LinkedList;
public class ListEx {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
LinkedList<String> li=new LinkedList<String>();// generic collection - FIFO- FCFS- First Come First Serve
li.add("Besant");
li.add("Technologies");
li.add("HSR Layout");
li.add("Sector-1");
li.add("Bangalore");
li.addFirst("India");
System.out.println("***********************************");
System.out.println("List Display" + li.toString());
System.out.println("**************************************");
li.removeFirst();
System.out.println("***********************************");
System.out.println("After Removal of First element" + li.toString());
System.out.println("**************************************");
li.remove();
System.out.println("***********************************");
System.out.println("After removal of an element" + li.toString());
System.out.println("**************************************");
li.addFirst("ttttt");
System.out.println("***********************************");
System.out.println("Adding element at first position" +li.toString());
System.out.println("**************************************");
System.out.println("Get elements of 2nd position " +li.get(2));
System.out.println("****Linked List items (Foreach Display)****************");
for(String d: li)
{
System.out.println(d);
}
System.out.println("********************************************************");
System.out.println("Linked List (Itertor Display)");
Iterator<String> iter=li.iterator();
while(iter.hasNext())
{
System.out.println(iter.next());
}
System.out.println("********************************************************");
}
}
Output:
***********************************
List Display[India, Besant, Technologies, HSR Layout, Sector-1, Bangalore]
**************************************
***********************************
After Removal of First element[Besant, Technologies, HSR Layout, Sector-1, Bangalore]
**************************************
***********************************
After removal of an element[Technologies, HSR Layout, Sector-1, Bangalore]
**************************************
***********************************
Adding element at first position[ttttt, Technologies, HSR Layout, Sector-1, Bangalore]
**************************************
Get elements of 2nd position HSR Layout
****Linked List items (Foreach Display)****************
ttttt
Technologies
HSR Layout
Sector-1
Bangalore
********************************************************
Linked List (Itertor Display)
ttttt
Technologies
HSR Layout
Sector-1
Bangalore
********************************************************
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Methods of LinkedList
| Method Name | Description |
| boolean add(E e) | Appends the element ‘e’ to the end of the list. |
| void add(int i, E e) | Inserts the element ‘e’ at the specified index ‘i’ in the list. |
| void addFirst(E e) | Inserts the element ‘e’ in the start of the list |
| void addLast(E e) | Inserts the element ‘e’ in the end of the list |
| void clear() | Removes all the elements from the list. |
| boolean contains(Object o) | Returns true if the list contains the object specified in the argument. |
| E get(int index) | Returns the element at the specified index in the list. |
| boolean isEmpty() | Returns true if the list has no elements |
| E remove(int index) | Removes the element at the specified index in the list. |
| E removeFirst() | Removes and returns the first element in the list. |
| boolean removeFirstOccurence(Object o) | Removes the first occurrence of the element in the list. |
| E removeLast() | Removes and returns the last element in the list. |
| boolean removeLastOccurence(Object o) | Removes the last occurrence of the element in the list (traversing from head to tail) |
| E set(int index, E element) | Replaces the element at the specified index in the list with the element given. |
| int size() | Returns the number of elements in the list. |
| peek() | Retrieves the element in the head, but does not remove. |
| E peekFirst() | Retrieves the first element of the list, but does not remove or returns null if this list is empty. |
| E peekLast() | Retrieves the last element of the list, but does not remove or returns null if this list is empty. |
| E poll() | Retrieves and removes the element in the head. |
| E pollFirst() | Retrieves and removes the first element of the list. |
| E pollLast() | Retrieves and removes the last element of the list. |
| E pop() | Pops an element from the list, considering the list as stack. |
| void push(E e) | Inserts the element e to the list, considering the list as stack. |
| boolean addAll(Collection<? extends E> c) | Appends all of the elements in the specified collection to the end of the list. |
| boolean removeAll(Collection<?> c) | Removes all the elements that are contained in the specified collection from the LinkedList. |
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