The Solution for the Problem is

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

 public static void main(String[] args) {
        Scanner s = new Scanner(System.in);
        int t = s.nextInt();
        String [] pair_left = new String[t];
        String [] pair_right = new String[t];
        
        for (int i = 0; i < t; i++) {
            pair_left[i] = s.next();
            pair_right[i] = s.next();
        }

//Write your code here
        HashSet<String> pairs = new HashSet<>();
        
        for(int i = 0 ; i < t; i++){
            String str = pair_left[i] + " " + pair_right[i];
            String rev = pair_right[i] + " " + pair_left[i];
            if(!pairs.contains(rev)){
                pairs.add(str);
            }
            System.out.println(pairs.size());
        }

   }
}

Test case #5 is wrong, At least it's conflicted with this problem's desc.

how solve this i failed from 1/6 test cases there is error show in test case 5 import java.io.; import java.util.; import java.text.; import java.math.; import java.util.regex.*;

public class Solution {

public static void main(String[] args) { Scanner s = new Scanner(System.in); int t = s.nextInt(); String [] pair_left = new String[t]; String [] pair_right = new String[t];

    for (int i = 0; i < t; i++) {
        pair_left[i] = s.next();
        pair_right[i] = s.next();
    }

// ... your previous code unchanged ... Set hashSet = new HashSet<>(); for (int i = 0; i < t; i++){ hashSet.add(pair_left[i]+" "+pair_right[i]);hoow System.out.println(hashSet.size()); } } }

Test case 5 is wrong. I want them to fix it.

Here is java Hashset solution - https://programmingoneonone.com/hackerrank-java-hashset-problem-solution.html