In this tutorial, we will see “How to find Duplicate Element in a Stream in Java 8?”. In order to find duplicates, we are going to use several techniques.  Find Duplicate Elements in a Stream in Java 8...!!! Click To Tweet

1. Find Duplicate Elements using ‘Set’

Set doesn’t allow duplicates and therefore return ‘false’ if the element is already present. 

Example

Output:
 

2. Find Duplicate Elements using ‘Collectors.groupingBy()’

Group the elements in a Map using Collectors.groupingBy and find elements if their occurrence is more than 1

Example

Output:
 

3. Find Duplicate Elements using ‘Collections.frequency()’

Filter the elements from the List whose occurrence is more than 1 using Collections.frequency() and then count those elements

Example

Output:
Find Duplicate Elements in a Stream in Java 8...!!! Click To Tweet Do you like this Post? – then check my other helpful posts:

Other Useful References: