Remove Duplicate Elements from Vector in Java Example

This example shows how to remove duplicate elements from Vector in Java. This example also shows how to remove duplicate elements using LinkedHashSet class and Java 8 Stream.

How to remove duplicate elements from Vector in Java?

There are a couple of ways using which we can remove duplicate elements from Vector in Java as given below.

1. Using the LinkedHashSet class

The Set in Java is a data structure does not allow duplicate elements. When we convert a vector object to such a Set object, only unique elements will be added to it. We can then clear the Vector object and add all elements of the Set back to the vector using the addAll method.

import java.util.LinkedHashSet;

import java.util.Vector;

public class VectorRemoveDuplicateElements {

public static void main(String[] args) {

Vector<Integer> vNumbers = new Vector<Integer>();

vNumbers.add(10);

vNumbers.add(20);

vNumbers.add(30);

vNumbers.add(20);

vNumbers.add(10);

* convert Vector to a LinkedHashSet object.

* Since the Set does not allow duplicate elements, only

* unique elements will be added to it.

LinkedHashSet<Integer> lhSet = new LinkedHashSet<Integer>( vNumbers );

//clear the vector

vNumbers.clear();

//add all unique elements back to the vector

vNumbers.addAll(lhSet);

System.out.println("Vector contains: " + vNumbers);

}

Output

1	Vector contains: [10, 20, 30]

Why convert the vector to LinkedHashSet and not HashSet? Well, the HashSet class does not guarantee the order of the elements. The order of the elements returned by the iterator of the HashSet may not stay constant over time. If you do not want to maintain the insertion order of the elements, you may use the HashSet class as well.

On the other hand, the LinkedHashSet class maintains a doubly-linked list running through its elements and returns the elements in the same order they were inserted into it. That is the reason I choose the LinkedHashSet over HashSet.

2. Using the Java 8 Stream

If you are using Java version 8 or later, you can also use the Java 8 stream to remove duplicate elements from Vector as given below.

Vector<Integer> vNumbers = new Vector<Integer>();

vNumbers.add(10);

vNumbers.add(20);

vNumbers.add(30);

vNumbers.add(20);

vNumbers.add(10);

vNumbers = vNumbers.stream().distinct().collect(Collectors.toCollection(Vector::new));

System.out.println("Vector contains: " + vNumbers);

Output

1	Vector contains: [10, 20, 30]

This example is a part of the Java Vector Tutorial with Examples.

Please let me know your views in the comments section below.

References:
Java 8 Vector Documentation

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Rahim

I have a master's degree in computer science and over 18 years of experience designing and developing Java applications. I have worked with many fortune 500 companies as an eCommerce Architect. Follow me on LinkedIn and Facebook.