#09 | Find Duplicate Elements in Array | 3 Ways (Java)
Java Program to Find Duplicate Elements in Array | Full Explanation
In this video, we learn how to find duplicate elements in an array using Java.
The same problem is solved using three different approaches, which are commonly asked in Java coding interviews.
🔹 Problem Statement
Given an integer array, find all the duplicate elements present in it.
Example:
Input: [1, 2, 3, 4, 4, 5, 5]
Output: [4, 5]
🔹 Method 1: Using Nested Loops (Brute Force)
In the first approach, we use two nested loops to compare each element with every other element in the array.
If two elements are equal, it means the element is a duplicate
The duplicate value is stored in a List
This method helps in understanding the basic comparison logic, but it is not efficient for large arrays.
🔹 Method 2: Using Set (Optimized Approach)
In the second method, we use a HashSet.
A Set does not allow duplicate elements
When we try to add an element that already exists, add() returns false
That element is identified as a duplicate
This approach is faster and commonly used in real-world Java applications.
🔹 Method 3: Using Stream API
In the third approach, we use Java Stream API.
The array is converted into a stream
Elements are grouped using groupingBy
counting() is used to count occurrences of each element
Elements with count greater than 1 are filtered as duplicates
This method is clean, modern, and interview-friendly.
🔹 Key Concepts Covered
Nested loops in Java
Set behavior and duplicate detection
Stream API with grouping and counting
Array to Stream conversion
This video is useful for Java beginners, coding practice, and interview preparation.
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