Radix sort with array of custom linked lists - error trying to print - arrays

Question

I have an assignment for class and we have to use a radix sort using an array of linked lists.
It should split a string into a key and value, and store them as an Entry.
public class Entry {
public String key;
public String value;
public Entry() {
}
public Entry(String key, String value) {
this.key = key;
this.value = value;
}
}
The Entry class is pretty basic, I dont think it has any problems.
The issue is that I can either get the while loop to iterate exactly once and then the program completely stops, or I can cause an infinite loop depending on whether or not I use array[10].removeHead() twice or not
import java.io.File; // Import the File class
import java.io.FileNotFoundException; // Import this class to handle errors
import java.util.Scanner; // Import the Scanner class to read text files
public class RadixSort {
public static void main(String[] args) {
try {
LinkedList[] array = new LinkedList[11];
for(int i = 0; i < 11; i++) {
array[i] = new LinkedList();
}
File myObj = new File("years.txt");
Scanner myReader = new Scanner(myObj);
int counter = Integer.parseInt(myReader.nextLine());
System.out.println(counter);
while (myReader.hasNextLine()) {
String string = myReader.nextLine();
if (string.equals("END")) break;
String[] parts = string.split(",");
String part1 = parts[0];
String part2 = parts[1];
Entry a = new Entry(part1, part2);
array[10].addTail(a);
//System.out.println(array[ 0].removeHead().key);
// this works, but gives null ptr exception^^^
System.out.println(array[10].peekHead().key + "," + array[10].peekHead().value);
array[10].removeHead();
}
for (int i = counter; i > 0; i--) {
while (!array[10].peekHead().key.contains(null)) {
String s = array[10].peekHead().key;
String g = array[10].peekHead().value;
int a = Integer.parseInt(s.substring(i-1));
System.out.println(a);
//System.out.println(s);
Entry bruh = new Entry(s, g);
array[a].addHead(bruh);
if (s.equals(null)) System.out.println("error");
//System.out.println(array[10].peekHead().key);
//System.out.println(array[a].peekHead().value);
array[10].removeHead();
System.out.println(array[a].peekHead().key);
}
for (int j = 0; j < 10; j++) {
while (!array[j].peekHead().key.equals(null)) {
array[10].addTail(array[j].removeHead());
}
}
}
while (!array[10].peekHead().key.equals(null)) {
System.out.println(array[10].peekHead().key + "," + array[10].peekHead().value);
array[10].removeHead();
}
myReader.close();
} catch (FileNotFoundException e) {
System.out.println("An error occurred.");
e.printStackTrace();
}
}
}
When I try to print it out it just prints the first Node a bunch of times and then throws a NullPointerException like below:
Exception in thread "main" java.lang.NullPointerException: Cannot invoke "java.lang.CharSequence.toString()" because "s" is null
at java.base/java.lang.String.contains(String.java:2054)
at RadixSort.main(RadixSort.java:34)
My linked list class should work fine, I did it for our first assignment and tested it pretty thoroughly and it had no errors that I could see.
I tried to just add a couple more removeHead() functions to see if that would change anything and it just keeps throwing that dumb null pointer exception. If anyone could help with anything I would be incredibly grateful.