/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		// your code goes here
		// arr = {56, 25, 13, 7, 56, 38, 7}
		// output {56, 7} // duplicates
		HashSet<Integer> set = new HashSet<>();
		int arr[] = new int[] {56, 25, 13, 7, 56, 38, 7};
		ArrayList<Integer> res = new ArrayList<>();
		for(int x: arr) {
			if(set.contains(x)) {
				res.add(x);
			}
			else {
				set.add(x);
			}
		}
 
		System.out.println(res);
 
	}
}

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