How to Sort HashSet in Java

In this post, we will see how to sort HashSet in java.

HashSet is a collection which does not store elements in any order. You might come across a situation where you need to sort HashSet.

There can be many ways to sort HashSet, we will see two methods here.

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Using TreeSet

You can use TreeSet to sort HashSet. As you know that TreeSet stores objects in ascending order by default.

package org.arpit.java2blog;

import java.util.HashSet;

import java.util.Set;

import java.util.TreeSet;

public class SortHashSetMain {

public static void main(String[] args) {

// Creating a new HashSet

Set<String> set = new HashSet<String>();

set.add("John");

set.add("Martin");

set.add("Andy");

set.add("Steve");

set.add("Mary");

System.out.println("Before Sorting:");

System.out.println(set);

* Use TreeSet to sort HashSet

TreeSet<String> sortedSet=new TreeSet<>(set);

System.out.println("==================================");

System.out.println("After Sorting:");

System.out.println(sortedSet);

}

When you run above program, you will get below output:

Before Sorting: [Steve, John, Martin, Andy, Mary] ================================== After Sorting: [Andy, John, Martin, Mary, Steve]

Using Collections’s sort

You can convert HashSet to List and then use Collections’s sort method to sort the HashSet.

package org.arpit.java2blog;

import java.util.ArrayList;

import java.util.Collections;

import java.util.HashSet;

import java.util.List;

import java.util.Set;

public class SortHashSetMain {

public static void main(String[] args) {

// Creating a new HashSet

Set<String> set = new HashSet<String>();

set.add("John");

set.add("Martin");

set.add("Andy");

set.add("Steve");

set.add("Mary");

System.out.println("Before Sorting:");

System.out.println(set);

/*Convert to list and then use sort method

List<String> nameList = new ArrayList<String>(set);

Collections.sort(nameList);

System.out.println("==================================");

System.out.println("After Sorting:");

System.out.println(nameList);

}

When you run above program, you will get below output:

Before Sorting:
[Steve, John, Martin, Andy, Mary] ==================================
After Sorting:
[Andy, John, Martin, Mary, Steve]

That’s all about how to sort HashSet in java.

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How to Sort HashSet in Java

Using TreeSet

Using Collections’s sort

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