Removing duplicates and ordering a list using java

Hi everyone, in this blog post, I will be writing about 'How to remove duplicates and order a list using java'.
For removing duplicates in a list, we can put all the contents of the list to a set. For ordering the set, we can use an implementation of treeset. So in general, to remove duplicates and order a set, we could do by putting all the contents of the list to a treeset. Please refer my post about sets to understand more about treesets.

Here is the java program to remove duplicates and order a list.

package com.blog.techjourney;

import java.util.ArrayList;
import java.util.List;
import java.util.Set;
import java.util.TreeSet;

public class removeDuplicatesAndOrder {

    public static void main(String[] args) {
        List countries = new ArrayList();
        
        countries.add("Canada");
        countries.add("Australia");
        countries.add("Brazil");
        countries.add("Canada");
        countries.add("Egypt");
        countries.add("Denmark");
        System.out.println(countries);
        removeDuplicatesAndOrder(countries);
        System.out.println(countries);
    }
    
    public static void removeDuplicatesAndOrder(List list)
    {
        Set treeset = new TreeSet();
        treeset.addAll(list);
        list.clear();
        list.addAll(treeset);
    }
}

The output of the following program is as follows. It will be in sorted order as well as it does not contain any duplicates.

[Canada, Australia, Brazil, Canada, Egypt, Denmark]
[Australia, Brazil, Canada, Denmark, Egypt]

Thank you for reading the post. Please comment below if you have any doubts. Any alternative solutions to remove duplicates and order a list is mostly welcome.

Related Topics:
1) Map and Sets in Java
2) Program to find the longest sequence in an array.