NullPointerException is killing me

Question

It comes after me with a chainsaw while I'm sleeping.
Alright, here's the briefing. I am working on a program called Radix Sort. This program analyzes the FIRST DIGIT of every number that is inputed by the user, and sorts it from least to greatest based on that digit. So if the user inputed 123, 321 and 582, the new sorted output will be 321, 582, 123. Then, the program will look at the SECOND DIGIT from the NEW OUTPUT, and sort it from least to greatest. The new output will be 321, 123, 582. It will the nlook at the THIRD DIGIT from the NEW OUTPUT, and sort it from least to greatest. The newest and final output will be 123, 321, 582. It is now sorted from least, to greatest completely.
However, the Java God decides to pull some tricks on me. This is what I get when I run the program.
How many numbers would you like it to sort? // This is the program asking the user
3 //This is my input
Please enter value 1. //Program asking user
452 //my input
Please enter value 2. //Program asking user
673 //my input
Please enter value 3. //yadda yadda
234 //you get the point
java.lang.NullPointerException
at radix.itemsToQueues (radix.java:45)
at radix.sort (radix.java:81)
at radix.main (radix.java:124)
at java.lang.VirtualMachine.invokeMain (VirtualMachine.java)
at java.lang.VirtualMachine.main (VirtualMachine.java:108)
Maybe I've been looking at the code too long now, but I can't point out why this error happens. So, if the community can help me out, I would be most thankful. Here is the code in question..
public class radix
     * @param number the number that is to be analyzed
     * @param n the nth digit of number being examined
    private static int getDigits(int number, int n)
        int length = 0;
        length = findNumLength(number);
        int tmp = 0;
        if(length < n+1)
            return tmp;
        else
            while(tmp < n)
                number = number/10;
                tmp++;
            tmp = number%10;
            return tmp;
    * @param nums an array containing the numbers inputed by user
    * @param n the nth digit being examined
    * @param max the amount of numbers in existance
   private static queue[] itemsToQueues(int[] nums, int n, int max)
      queue[] ques;
      ques = new queue[10];
      int tmp = 0;
      for(int i = 0; i < max; i++)
          tmp = getDigits(nums, n);
ques[tmp].enqueue(new Integer(nums[i]));
return ques;
private static int[] queuesToArray(queue[] ques, int max)
int[] nums; //recreating the array
nums = new int[max];
int tmp = 0;
for(int i = 0; i < max; i++)
while(ques[i].isEmpty() == false)
nums[tmp] = ((Integer) ques[i].dequeue()).intValue();
tmp++;
return nums;
* @param nums an array containing the numbers inputed by user
* @param numDigits the maximum amount of digits there are
* @param max the amount of numbers in existance
public static int[] sort(int[] nums, int numDigits, int max)
queue[] ques;
ques = new queue[10];
int n = 0; //nth digit
do
ques = itemsToQueues(nums, n, max);
nums = queuesToArray(ques, max);
n++;
}while(n < numDigits);
return nums;
private static int findNumLength(int num)
int length = 0;
do
num = num/10;
length++;
}while(num != 0);
return length;
public static void main(String[] args)
int[] nums; //the array that holds the numbers inputed by the user
int max = 0; // the amount of numbers the user will input
int numDigits = 0; //the maximum amount of digits there are
System.out.println("How many numbers would you like it to sort?");
max = input.getInt();
nums = new int[max];
for(int i = 0; i < max; i++)
System.out.println("Please enter value " + (i+1) + ".");
nums[i] = input.getInt();
if(nums[i] > numDigits)
numDigits = nums[i];
numDigits = findNumLength(numDigits);
nums = sort(nums, numDigits, max);
Thanks guys!

Answer 1

Here are some of the other classes that are used in the program..
input.java
import java.io.*;
public class input
    public static int getInt()
        String input = "";
        int result = 0;
        boolean check = true;
        do
            try
                BufferedReader console = new BufferedReader(new InputStreamReader(System.in));
                input = console.readLine();
                result = Integer.parseInt(input);
            catch(IOException ioex)
                System.out.println("Input error! Please try again.");
                check = false;
            catch(NumberFormatException nfex)
                System.out.println("Input error! Please use integers!");
                check = false;
        }while(check == false);
        return result;
}queue.java
public interface queue
    boolean isEmpty();
    void enqueue(Object x);
    Object dequeue();
    Object peekFront();
}list_queue.java
import java.util.LinkedList;
public class ListQueue implements queue
    private LinkedList items;
    public ListQueue()
        items = new LinkedList();
    public boolean isEmpty()
        return items.isEmpty();
    public void enqueue(Object x)
        items.addLast(x);
    public Object dequeue()
        return items.removeFirst();
    public Object peekFront()
        return items.getFirst();
}Thanks again!