code: import java.nio.file.*;
  import java.util.*;
  
  public class Semordnilap {
  
      public static void main(String[] args) throws Exception {
          List<String> lst = Files.readAllLines(Paths.get("unixdict.txt"));
          Set<String> seen = new HashSet<>();
          int count = 0;
          for (String w : lst) {
              w = w.toLowerCase();
              String r = new StringBuilder(w).reverse().toString();
              if (seen.contains(r)) {
                  if (count++ < 5)
                      System.out.printf("%-10s %-10s\n", w, r);
              } else seen.add(w);
          }
          System.out.println("\nSemordnilap pairs found: " + count);
      }
  }
  