Method Is Not Returning Array - Null Error

I am trying to return an array and I keep getting a null error. The below class sets the material numbers into an array and should return that array if called :

public class Jobs {
private int[] materialsNumber;
//change to parts and create another class that gets the materials for the parts
 public int[] job1() {
materialsNumber[0] = 11960120;

[Code] ....

I later try to call the method. The program executes but stops after I println "test in loop"

public class PurchaseOrdersToParts {
 private Jobs job = new Jobs();
 int[] getPartsForPurchaseOrder(BigDecimal purchaseOrder) {
 System.out.println("inside getparts");
 BigDecimal testNum = new BigDecimal(123.0);
 
[Code] ....

This is the method that is calling the method in the GenerateOrdersToParts class

private PurchaseOrdersToParts purchaseOrdersToParts = new PurchaseOrdersToParts();
 @Inject
PoRepository poRepository;
public GenerateShopJobTickets() {
 
[Code] .....