I've looked through several solutions and I'm quite surprised. If the problem involves handling pairs and they're already split into two arrays, why combine them back into a single string? Instead, there's a more elegant approach using the SimpleEntry class. You can simply use

Set<AbstractMap.SimpleEntry<String, String>> uniquePairs = new HashSet<>();

to handle the pairs directly.

hi guys i think converting the both arrays into string and adding it into a set is much easy process

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();
    }
    Set<String> nameSet = new HashSet<>();
    for(int i =0; i<t; i++){
        String str = pair_left[i]+" "+pair_right[i];
        nameSet.add(str);
        System.out.println(nameSet.size());
    }
}

}

import java.io.; import java.util.;

public class Solution {

public static void main(String[] args) {
    Scanner sc=new Scanner(System.in);
    int n=sc.nextInt();
    sc.nextLine();
    Set<String> set=new HashSet<>();
    for(int i=0;i<n;i++){
        String str1=sc.nextLine();
        set.add(str1);
       System.out.println(set.size());  
    }

    sc.close();
}

}

    Set<String> set=new LinkedHashSet<>();
    String x;

     for(int i=0;i<pair_left.length;i++){
         x="";
         x=pair_left[i]+" "+pair_right[i];
         set.add(x);
         System.out.println(set.size());
     }