Add, remove, retain, sort methods of linkedlist collection (java / example)

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What is LinkedList collection?

  • The LinkedList class extends AbstractSequentialList and implements the List interface.
  • Important methods of LinkedList collection?
    • Remove
    • Add
    • Retain
    • Sort
    • Iterate
    • Get
    • Contains And
    • Clear

Program – Add, remove, retain, sort methods of linkedlist

package org.learn.collection.list.linkedlist;

import java.util.Collections;
import java.util.LinkedList;
import java.util.ListIterator;

public class DemoLinkedList {

 public static void main(String[] args) {
  LinkedList<String> linkedList = new LinkedList<>();
  linkedList.add("archery");
  linkedList.add("badminton");
  linkedList.add("canoe");
  linkedList.add("boxing");
  linkedList.add("canoe");
  linkedList.add("diving");
  linkedList.add("badminton");
  linkedList.add("diving");

  System.out.println("Demo of remove methods: ");
  demoRemoveMethod(linkedList);

  System.out.println("\nDemo of add methods: ");
  demoAddMethod(linkedList);

  System.out.println("\nDemo of retain method: ");
  demoRetainAll(linkedList);

  System.out.println("\nSort elements of linkedList: ");
  demoSortMethod(linkedList);

  System.out.println("\nIterate through linkedList: ");
  demoIterateMethod(linkedList);

  //[golf, diving, archery]
  System.out.println("\nDemo of get method of linkedlist: ");
  //golf
  System.out.println("Element at index 0: " + linkedList.get(0));
  //archery
  System.out.println("Element at index 2: " + linkedList.get(2));

  //[golf, diving, archery]
  System.out.println("\nDemo of contains method of linkedlist: ");
  System.out.println("Check linkedlist contains diving: " + linkedList.contains("diving"));
  System.out.println("Check linkedlist contains judo: " + linkedList.contains("judo"));

  System.out.println("\nDemo of clear method of linkedlist: ");
  linkedList.clear();
  System.out.println("Clear linkedList: " + linkedList);
 }

 private static void demoRemoveMethod(LinkedList<String> linkedList) {
  // [archery, badminton, canoe, boxing, diving, badminton, diving]
  System.out.println("Orignal LinkedList:" + linkedList);

  // Remove element by index
  String removedElement = linkedList.remove(2);
  // [archery, badminton, boxing, diving, badminton, diving]
  System.out.printf("1. Removed element %s from index 2: %s \n", removedElement, linkedList);

  // Remove element by index
  removedElement = linkedList.removeFirst();
  // [badminton, boxing, diving, badminton, diving]
  System.out.printf("2. Removed first element %s of linked list:%s \n", removedElement, linkedList);

  // Remove element by index
  removedElement = linkedList.removeLast();
  // [badminton, boxing, diving, badminton]
  System.out.printf("3. Removed last element %s of linked list:%s \n", removedElement, linkedList);

  // Remove element after comparing and remove it
  linkedList.remove("boxing");
  // [badminton, diving, badminton]
  System.out.println("4. Removed boxing from linkedList: " + linkedList);

  LinkedList<String> removeElementsList = new LinkedList<>();
  removeElementsList.add("diving");

  // Remove element by supplying another collection
  linkedList.removeAll(removeElementsList);

  // [badminton, badminton]
  System.out.println("5. Removed collection containing diving: " + linkedList);

  // Remove element by supplying another collection
  linkedList.removeLastOccurrence("badminton");

  // [badminton, badminton]
  System.out.println("6. Removed last occurence of badminton: " + linkedList);

  // Remove element by supplying another collection
  linkedList.removeFirstOccurrence("badminton");

  // [badminton, badminton]
  System.out.println("7. Removed first occurence of badminton: " + linkedList);
 }

 private static void demoAddMethod(LinkedList<String> linkedList) {
  // [canoe]
  System.out.println("1. Orignal LinkedList:" + linkedList);
  linkedList.add(0, "archery");
  linkedList.add(2, "canoe");
  // [archery, canoe, canoe]
  System.out.println("2. Added element at 0 and 2 index: " + linkedList);

  linkedList.add("diving");
  // [archery, canoe, canoe, diving]
  System.out.println("3. Added element in list: " + linkedList);

  LinkedList<String> addElementsList = new LinkedList<>();
  addElementsList.add("squash");
  addElementsList.add("bowling");

  // It will add elements to last of list
  linkedList.addAll(addElementsList);
  // [archery, canoe, canoe, diving, squash, bowling]
  System.out.println("4. Added another list : " + linkedList);

  LinkedList<String> anotherList = new LinkedList<>();
  anotherList.add("golf");
  anotherList.add("judo");

  // It will add elements from index 1
  linkedList.addAll(1, anotherList);
  // [archery, golf, judo, canoe, canoe, diving, squash, bowling]
  System.out.println("5. Added another list at index 1 : " + linkedList);

  // It will add element before head i.e. first element of list of list
  linkedList.addFirst("squash");
  //  [squash, archery, golf, judo, canoe, canoe, diving, squash, bowling]
  System.out.println("6. Added element before head : " + linkedList);

  // It will add elements to last of list
  linkedList.addLast("judo");
  // [squash, archery, golf, judo, canoe, canoe, diving, squash, bowling, judo]
  System.out.println("7. Added element to after tail node : " + linkedList);
 }

 private static void demoRetainAll(LinkedList<String> linkedList) {
  // [squash, archery, golf, judo, canoe, canoe, diving, squash, bowling, judo]
  System.out.println("Orignal LinkedList:" + linkedList);
  LinkedList<String> retainSportsList = new LinkedList<>();
  retainSportsList.add("golf");
  retainSportsList.add("diving");
  retainSportsList.add("archery");
  retainSportsList.add("badminton");
  System.out.println("Elements to be retained:"+retainSportsList);
  linkedList.retainAll(retainSportsList);
  //[archery, golf, diving]
  System.out.println("Elements retained in orignal linkedlist: " + linkedList);
 }

 private static void demoSortMethod(LinkedList<String> linkedList) {
  //[archery, golf, diving]
  System.out.println("Orignal LinkedList:" + linkedList);
  Collections.sort(linkedList);
  // [archery, diving, golf]
  System.out.println("1. Sort ascending order: " + linkedList);

  Collections.sort(linkedList, Collections.reverseOrder());
  // [golf, diving, archery]
  System.out.println("2. Sort desending order: " + linkedList);
 }

 private static void demoIterateMethod(LinkedList<String> linkedList) {

  System.out.println("1. Iterating using forEachRemaining:");
  // Output of for loop:
  // golf diving archery 
  linkedList.forEach(element -> System.out.printf("%s ", element));

  System.out.println("\n2. Iterating linkedList using foreach loop:");
  // Output of for loop:
  // golf diving archery 
  for (String element : linkedList) {
   System.out.printf("%s ", element);
  }

  System.out.println("\n3. Iterating linkedList using iterator:");
  ListIterator<String> listIterator = linkedList.listIterator();
  // Output of while loop:
  // golf diving archery 
  while (listIterator.hasNext()) {
   System.out.printf("%s ", listIterator.next());
  }
  System.out.println("");
 }

}

Output – Add, remove, retain, sort etc. methods of linkedlist

Demo of remove methods: 
Orignal LinkedList:[archery, badminton, canoe, boxing, canoe, diving, badminton, diving]
1. Removed element canoe from index 2: [archery, badminton, boxing, canoe, diving, badminton, diving] 
2. Removed first element archery of linked list:[badminton, boxing, canoe, diving, badminton, diving] 
3. Removed last element diving of linked list:[badminton, boxing, canoe, diving, badminton] 
4. Removed boxing from linkedList: [badminton, canoe, diving, badminton]
5. Removed collection containing diving: [badminton, canoe, badminton]
6. Removed last occurence of badminton: [badminton, canoe]
7. Removed first occurence of badminton: [canoe]

Demo of add methods: 
1. Orignal LinkedList:[canoe]
2. Added element at 0 and 2 index: [archery, canoe, canoe]
3. Added element in list: [archery, canoe, canoe, diving]
4. Added another list : [archery, canoe, canoe, diving, squash, bowling]
5. Added another list at index 1 : [archery, golf, judo, canoe, canoe, diving, squash, bowling]
6. Added element before head : [squash, archery, golf, judo, canoe, canoe, diving, squash, bowling]
7. Added element to after tail node : [squash, archery, golf, judo, canoe, canoe, diving, squash, bowling, judo]

Demo of retain method: 
Orignal LinkedList:[squash, archery, golf, judo, canoe, canoe, diving, squash, bowling, judo]
Elements to be retained:[golf, diving, archery, badminton]
Elements retained in orignal linkedlist: [archery, golf, diving]

Sort elements of linkedList: 
Orignal LinkedList:[archery, golf, diving]
1. Sort ascending order: [archery, diving, golf]
2. Sort desending order: [golf, diving, archery]

Iterate through linkedList: 
1. Iterating using forEachRemaining:
golf diving archery 
2. Iterating linkedList using foreach loop:
golf diving archery 
3. Iterating linkedList using iterator:
golf diving archery 

Demo of get method of linkedlist: 
Element at index 0: golf
Element at index 2: archery

Demo of contains method of linkedlist: 
Check linkedlist contains diving: true
Check linkedlist contains judo: false

Demo of clear method of linkedlist: 
Clear linkedList: []

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