收到此错误--java.util.NoSuchElementException: No line found- on line 20,27, and 34

Question

How do I fix this error?

java.util.NoSuchElementException: No line found.

I looked at other similar posts but couldn't figure out what to do with the solution. It looks (to me) like every sc.nextLine(); had a corresponding line with it.

Important Code is below Sorry, for the bad fromatting/Understanding. Its my first time here and I just started getting into programming.

package assignment2;
import java.util.Scanner;

public class StringToolsTester {

   public static void main(String[] args) {
       StringTools obj = new StringTools();
       
       
       //Method to get the reverse of the users string input
       Scanner s = new Scanner(System.in);
       System.out.print("reverse - Enter Any String: ");
       String z = s.nextLine();
       System.out.println("Reversed String: "+obj.reverse(z));
       s.close();
       
       //Method to get initials of the users string input
       Scanner a = new Scanner(System.in);
       System.out.print("initials - Enter Full Name: ");
       String initial = a.nextLine();
       System.out.println("Initials: "+obj.initials(initial));
       a.close();
      
       //Method to get the most frequent character from the users string input
       Scanner b = new Scanner(System.in);
       System.out.print("mostFrequent - Enter String: ");
       String most = b.nextLine();
       System.out.println("Most frequent character = "+obj.mostFrequent(most));
       b.close();
      
       //Method to get the binary equivalent of the users binary string input
       Scanner c = new Scanner(System.in);
       System.out.print("binaryToDecimal - Enter Binary: ");
       String str = c.nextLine();
       System.out.println(StringTools.binaryToDecimal(str));
       c.close();