In this article, we will discuss how to sort contents of LinkedList in ascending order containing only unique elements
1. Approach :
- Convert LinkedList into TreeSet which stores elements in default natural ordering for String objects
- Also, TreeSet allows only unique elements and maintains ascending-order
2. To sort LinkedList contents in ascending-order :
Steps:
- Iterate through ArrayList to check duplicate elements
- Create TreeSet using inter-conversion collection constructors
- Add ArrayList object to TreeSet’ constructor-argument
- Again, iterate through TreeSet which stores only unique elements
- Note: If NULL is present; NullPointerException will be thrown (starting Java 1.7 version)
SortingLinkedListContentsInAscendingOrder.java
package in.bench.resources.java.collections;
import java.util.LinkedList;
import java.util.TreeSet;
public class SortingLinkedListContentsInAscendingOrder {
public static void main(String[] args) {
// creating LinkedList object of type String
LinkedList<String> companies = new LinkedList<String>();
// adding elements to LinkedList object
companies.add("Oracle");
companies.add("Google");
companies.add("LinkedIn");
companies.add("Facebook");
companies.add("Oracle");
companies.add("Amazon");
companies.add("Google");
// Iterating using enhanced for-loop
System.out.println("Before Sorting : Insertion Order\n");
for(String company : companies) {
System.out.println(company);
}
// convert to TreeSet
TreeSet<String> ts = new TreeSet<String>(companies);
// reverse order of LinkedList contents
System.out.println("\n\n\nTreeSet : unique elements "
+ "and ascending order\n");
for(String company : ts) {
System.out.println(company);
}
}
}
Output:
Before Sorting : Insertion Order
Oracle
Google
LinkedIn
Facebook
Oracle
Amazon
Google
TreeSet : unique elements and ascending order
Amazon
Facebook
Google
LinkedIn
Oracle
From above example, LinkedList
- allows duplicate elements
- null object is allowed
- while iterating insertion-order is maintained
From above example, TreeSet
- doesn’t allow duplicate elements
- while iterating, retrieve elements in ascending-order
Related Articles:
- Java – Conversion of List to Map
- Java – Conversion of Map to List
- Java – Conversion of Arrays to List
- Java – Conversion of List to Arrays
- Java 8 – Conversion of List to Map
- Java 8 – Conversion of Map to List
- Java 8 – Conversion of Arrays to List
- Java 8 – Conversion of List to Arrays
- Java 8 – How to convert HashMap to ArrayList ?
- Java – Conversion of ArrayList to Arrays in 2 ways
- Java – Conversion of Arrays to Vector
- Java – Conversion of Arrays to HashSet
- Java – Conversion of HashSet to Arrays
- Java – Conversion of LinkedList into Vector
- Java – Conversion of ArrayList into HashSet to remove duplicate elements
- Java – How to convert LinkedList to contain unique elements in ascending-order ?
- Java – Converting Ordered ArrayList into Sorted TreeSet
- Java – How to remove elements while iterating collection object ?
References:
- https://docs.oracle.com/javase/tutorial/collections/intro/
- https://docs.oracle.com/javase/tutorial/collections/interfaces/collection.html
- https://docs.oracle.com/javase/7/docs/api/java/util/Collection.html
- https://docs.oracle.com/javase/tutorial/collections/interfaces/list.html
- https://docs.oracle.com/javase/7/docs/api/java/util/LinkedList.html
- https://docs.oracle.com/javase/8/docs/api/java/util/List.html
- https://docs.oracle.com/javase/tutorial/collections/interfaces/order.html
- https://docs.oracle.com/javase/7/docs/api/java/util/Collections.html
Happy Coding !!
Happy Learning !!
