Java 8 remove duplicates from List

In this tutorials, I am going to show you how to remove duplicate elements from the list using Java 8 syntax.

How to remove duplicates from list :

Here I am creating a Department class, it holds department details.

Department.java

public class Department { private int deptId; private String deptName; public Department[int deptId, String deptName] { super[]; this.deptId = deptId; this.deptName = deptName; } public int getDeptId[] { return deptId; } public void setDeptId[int deptId] { this.deptId = deptId; } public String getDeptName[] { return deptName; } public void setDeptName[String deptName] { this.deptName = deptName; } }

We can remove the duplicate elements from a list in following 2 different ways.

Removing Duplicates by assigning List to TreeSet :

Preparing a list containing duplicate Department objects, and remove those duplicate departments using Java8 stream.

Here to remove the duplicate elements, by assigning a list to TreeSet. As TreeSet doesnt allow the duplicate elements, it removes.

import java.util.ArrayList; import java.util.Comparator; import java.util.List; import java.util.Set; import java.util.TreeSet; import java.util.stream.Collectors; public class RemoveDuplicates { public static void main[String[] args] { List deptList = new ArrayList[]; deptList.add[new Department[1, "IT"]]; deptList.add[new Department[2, "HR"]]; deptList.add[new Department[1, "IT"]]; deptList.add[new Department[4, "Development"]]; deptList.add[new Department[2, "HR"]]; // Removing the Elements by assigning list to TreeSet Set deptSet = deptList.stream[] .collect[Collectors.toCollection[[] -> new TreeSet[Comparator.comparing[Department::getDeptName]]]]; deptSet.forEach[dept -> System.out.println["DeptId [" + dept.getDeptId[] + "] Name :" + dept.getDeptName[]]]; } }

Output :

DeptId [4] Name :Development DeptId [2] Name :HR DeptId [1] Name :IT

Removing Duplicates using removeif[]:

import java.util.ArrayList; import java.util.HashSet; import java.util.List; import java.util.Set; public class RemoveDuplicates { public static void main[String[] args] { List deptList = new ArrayList[]; deptList.add[new Department[1, "IT"]]; deptList.add[new Department[2, "HR"]]; deptList.add[new Department[1, "IT"]]; deptList.add[new Department[4, "Development"]]; deptList.add[new Department[2, "HR"]]; Set deptSet = new HashSet[]; // directly removing the elements from list if already existed in set deptList.removeIf[p -> !deptSet.add[p.getDeptName[]]]; deptList.forEach[dept->System.out.println[dept.getDeptId[] +" : "+dept.getDeptName[]]]; } }

Output :

1 : IT 2 : HR 4 : Development

Happy Learning