জাভা keySet

import java.util.Collection;
import java.util.HashMap;
import java.util.Map;

public class Main {
  public static void main(String[] args) {
  Map<String, String> user = new HashMap<>();
  user.put("নাম", "মোঃ আরিফ");
  user.put("দেশ", "বাংলাদেশ");

  Collection<String> result = user.keySet();

  System.out.println(result);
  }
}