``````package dto;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

/**
* Java Program to find duplicate elements in an array. There are two straight
* forward solution of this problem first, brute force way and second by using
* HashSet data structure. A third solution, similar to second one is by using
* hash table data structure e.g. HashMap to store count of each element and
* print element with count 1.
*
* @author java67
*/

public class DuplicatesInArray{

public static void main(String args[]) {

String[] names = { "Java", "JavaScript", "Python", "C", "Ruby", "Java" };

// First solution : finding duplicates using brute force method
System.out.println("Finding duplicate elements in array using brute force method");
for (int i = 0; i < names.length; i++) {
for (int j = i + 1; j < names.length; j++) {
if (names[i].equals(names[j]) ) {
// got the duplicate element
}
}
}

// Second solution : use HashSet data structure to find duplicates
System.out.println("Duplicate elements from array using HashSet data structure");
Set<String> store = new HashSet<>();

for (String name : names) {
System.out.println("found a duplicate element in array : "
+ name);
}
}

// Third solution : using Hash table data structure to find duplicates
System.out.println("Duplicate elements from array using hash table");
Map<String, Integer> nameAndCount = new HashMap<>();

// build hash table with count
for (String name : names) {
Integer count = nameAndCount.get(name);
if (count == null) {
nameAndCount.put(name, 1);
} else {
nameAndCount.put(name, ++count);
}
}

// Print duplicate elements from array in Java
Set<Entry<String, Integer>> entrySet = nameAndCount.entrySet();
for (Entry<String, Integer> entry : entrySet) {

if (entry.getValue() > 1) {
System.out.println("Duplicate element from array : "
+ entry.getKey());
}
}
}
}
Output :
Finding duplicate elements in array using brute force method
Duplicate elements from array using HashSet data structure
found a duplicate element in array : Java
Duplicate elements from array using hash table
Duplicate element from array : Java// Uses a set, which does not allow duplicates

for (String name : names) {