我有一个菜单系统，我想使用addNewSupplier方法创建一个新供应商，然后使用printAllSuppliers方法与其他现有供应商一起打印新供应商的详细信息。但是当我尝试将其打印出来时，只显示现有的供应商，我想添加的新供应商显示了这个java.lang.NullPointerException。
package part01;
import java.util.ArrayList;
import java.util.Scanner;
public class mainMenu {
private static Scanner mySc = new Scanner(System.in);
private static ArrayList<Supplier> suppliers = new ArrayList<Supplier>();
public static void main(String[] args) {
Supplier s1 = systemData.sysData1();
Supplier s2 = systemData.sysData2();
Supplier s3 = systemData.sysData3();
Supplier s4 = systemData.sysData4();
suppliers.add(s1);
suppliers.add(s2);
suppliers.add(s3);
suppliers.add(s4);
runMenu();
}
private static void runMenu() {
System.out.println("---MAIN MENU---");
System.out.println();
System.out.println("1: Print all Supplier Infomation");
System.out.println("2: Add New Supplier");
System.out.println("3: Add New Product");
System.out.println("4: Add New Address");
System.out.println("5: Shutdown Application");
System.out.println();
System.out.print("Please Enter Menu Option: ");
while(!mySc.hasNextInt()) {
mySc.nextLine();
System.out.println("Must enter a valid number, please try again.");
System.out.print("Please Enter Menu Option: ");
System.out.println();
}
int menuChoice = mySc.nextInt(); mySc.nextLine();
switch(menuChoice) {
case 1: printAllSuppliers(); break;
case 2: addNewSupplier(); break;
case 3: addNewProduct(); break;
case 4: addNewAddress(); break;
case 5: systemExit(); break;
default:
System.out.println("");
System.out.println("Invalid input, please enter valid option.");
System.out.println();
runMenu();
}
}
private static void printAllSuppliers() {
System.out.println();
System.out.println("---PRINT ALL SUPPLIER DETAILS---");
System.out.println();
for (Supplier eachS : suppliers) {
eachS.printAllSupDe();
eachS.printProductList();
System.out.println();
}
System.out.print("--To return to the Main Menu please enter any key--");
if (mySc.hasNextLine()) {
mySc.nextLine();
runMenu();
}
}
private static void addNewSupplier() {
System.out.println();
System.out.println("---ADD NEW SUPPLIER---");
System.out.println();
System.out.println("Please enter your supplier name: ");
String supName = mySc.nextLine();
System.out.println("What product will you make?");
String supMake = mySc.nextLine();
System.out.println("Please enter your supplier code: ");
double supCode = mySc.nextDouble();
mySc.nextLine();
Address supAdd = addressValidation("Please enter address: ");
System.out.println();
System.out.println("Where will your company be based in?");
System.out.println();
SupRegion[] regionVal = SupRegion.values();
for (int i = 0; i < regionVal.length; i++) {
System.out.println((i+1) + ": " + regionVal[i]);
}
System.out.println();
System.out.println("Choose a value: ");
SupRegion areas = null;
int regionOption = mySc.nextInt()-1; mySc.hasNextLine();
System.out.println();
switch (regionOption) {
case 0: areas = part01.SupRegion.UNITED_KINGDOM; break;
case 1: areas = part01.SupRegion.OUTSIDE_EU; break;
case 2: areas = part01.SupRegion.EUROPE; break;
default:
System.out.println("Please select a valid option");
}
ArrayList<Product> noStock = new ArrayList<Product>();
Supplier s = new Supplier(supName, supMake, supAdd, areas ,supCode, noStock);
suppliers.add(s);
mySc.nextLine();
System.out.println("Your details have been successfully recorded!");
System.out.println("Enter any value to return to the Main Menu: ");
if (mySc.hasNextLine()) {
mySc.nextLine();
runMenu();
}
}
private static void addNewProduct() {
System.out.println("");
System.out.println("---ADD NEW PRODUCT---");
System.out.println("");
System.out.println("What type of product are you making?");
String proMake = mySc.nextLine();
System.out.println("What is name of the product?");
String proModel = mySc.nextLine();
System.out.println("Please enter the product code: ");
int proCode = mySc.nextInt();
System.out.println("How many are you selling?");
int proQuantity = mySc.nextInt();
System.out.println("Please enter the price of the product: ");
int proPrice = mySc.nextInt(); mySc.nextLine();
System.out.println();
boolean proDiscontinued = false;
Product p = new Product(proCode, proMake, proModel, proPrice, proQuantity, proDiscontinued);
System.out.println("Which supplier is your product from?");
for (int i = 0 ; i < suppliers.size(); i++) {
System.out.println((i + 1) + ": ");
suppliers.get(i).printAllSupDe();
}
System.out.println();
System.out.println("Enter the supplier number: ");
int supNo = mySc.nextInt(); mySc.nextLine();
Supplier S = suppliers.get(supNo-1);
S.getSupProduct().add(p);
System.out.println();
System.out.println("Your details have been successfully recorded!");
System.out.println("Enter any value to return to the Main Menu: ");
if (mySc.hasNextLine()) {
mySc.nextLine();
runMenu();
}
}
private static void addNewAddress() {
System.out.println("");
System.out.println("---ADD NEW ADDRESS---");
System.out.println("");
System.out.println("Please enter your address number: ");
int addNum = mySc.nextInt();mySc.hasNextLine();
System.out.println("Please enter your address town: ");
String addTo = mySc.nextLine();mySc.hasNextLine();
System.out.println("Please enter your address street: ");
String addStr = mySc.nextLine();mySc.hasNextLine();
System.out.println("Please enter your address postcode: ");
String addPc = mySc.nextLine();mySc.hasNextLine();
System.out.println("What country are you based in?");
String addCo = mySc.nextLine();
Address a = new Address(addNum,addTo,addStr,addPc,addCo);
System.out.println("Pick a supplier to change address?");
for (int i = 0 ; i < suppliers.size(); i++) {
System.out.println((i + 1) + ": ");
suppliers.get(i).printAllSupDe();
}
for (int i = 0; i < suppliers.size(); i++) {
System.out.println("Enter the supplier number: ");
int dealerNo = mySc.nextInt()-1; mySc.nextLine();
Supplier S = suppliers.get(dealerNo);
S.setSupAddress(a);
System.out.println("");
System.out.println("Your details have been successfully recorded!");
System.out.println("------------------------------------------------------");
System.out.println("Enter any value to return to the Main Menu: ");
System.out.println();
if (mySc.hasNextLine()) {
mySc.nextLine();
runMenu();
}
}
}
public static Address addressValidation(String string) {
String add1;
boolean addS= false;
do {
System.out.print(string);
add1 = mySc.nextLine();
if (add1.length() == 0) {
System.out.println("No value has been entered");
} else if (add1.length() > 7 || add1.length() < 7) {
System.out.println("");
System.out.println("Invalid input, input must have 7 characters.");
} else {
addS = true;
}
} while (!addS);
return null;
}
private static void systemExit() {
System.out.println();
System.out.println("The application has been terminated.");
System.out.println();
System.exit(0);
}
}
package part01;
import java.util.ArrayList;
public class Supplier {
private String supMake;
private String supName;
private Address supAddress;
private SupRegion supRegion;
private double supCode;
private ArrayList<Product> supProduct = new ArrayList<Product>();
public Supplier(String supMake, String supName, Address supAddress, SupRegion supRegion, double supCode,
ArrayList<Product> supProduct) {
super();
this.supMake = supMake;
this.supName = supName;
this.supAddress = supAddress;
this.supRegion = supRegion;
this.supCode = supCode;
this.supProduct = supProduct;
}
public void printAllSupDe() {
System.out.println("Supplier information: " + "|" + supMake + "| " + supName + " operated in " + supAddress.getFullAddress());
System.out.println("--------------------------------------------------------------------------------------------");
}
public void printProductList() {
for(Product eachPro : supProduct) {
eachPro.getProductDetails();
}
}
public String getSupMake() {
return supMake;
}
public void setSupMake(String supMake) {
this.supMake = supMake;
}
public String getSupName() {
return supName;
}
public void setSupName(String supName) {
this.supName = supName;
}
public Address getSupAddress() {
return supAddress;
}
public void setSupAddress(Address supAddress) {
this.supAddress = supAddress;
}
public SupRegion getSupRegion() {
return supRegion;
}
public void setSupRegion(SupRegion supRegion) {
this.supRegion = supRegion;
}
public double getSupCode() {
return supCode;
}
public void setSupCode(double supCode) {
this.supCode = supCode;
}
public ArrayList<Product> getSupProduct() {
return supProduct;
}
public void setSupProduct(ArrayList<Product> supProduct) {
this.supProduct = supProduct;
}
}