在我的ShoppingCart类中，我无法使用方法add()向我的newCart对象数组添加订单。相反，我收到以下错误：
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
at ShoppingCart.add(ShoppingCart.java:25)
at ShoppingCart.main(ShoppingCart.java:99)
我想不出一种方法来评估元素是否已插入到我的数组中，以及数组索引的确切位置错误。
我应该在ShoppingCart方法中声明新的add()对象吗？目前，我正在使用main（）来测试方法。
这是我的IceCreamOrder课程：
import java.util.Scanner; //Used to read user input from keyboard
import java.text.DecimalFormat; //Used to format output of decimal values
public class IceCreamOrder
{
//Private instance variable declarations
private String flavor;
private String vessel;
private String amount;
private double unitPrice;
private int quantity;
//Constructor declarations
public IceCreamOrder(String flavor, String vessel, String amount, double unitPrice, int quantity)
{
this.flavor = flavor;
this.vessel = vessel;
this.amount = amount;
this.unitPrice = unitPrice;
this.quantity = quantity;
}
public IceCreamOrder(String flavor, String vessel, String amount, double unitPrice)
{
this.flavor = flavor;
this.vessel = vessel;
this.amount = amount;
this.unitPrice = unitPrice;
this.quantity = 1;
}
public IceCreamOrder()
{
this.flavor = "";
this.vessel = "";
this.amount = "";
this.unitPrice = 0.0;
this.quantity = 0;
}
//Calculates the total price of order
public double price()
{
return quantity * unitPrice;
}
//Accessor method declarations
public String getFlavor()
{
return flavor;
}
public String getVessel()
{
return vessel;
}
public String getAmount()
{
return amount;
}
public double getUnitPrice()
{
return unitPrice;
}
public int getQuantity()
{
return quantity;
}
//Mutator method declarations
public void setFlavor(String flavor)
{
this.flavor = flavor;
}
public void setVessel(String vessel)
{
this.vessel = vessel;
}
public void setAmount(String amount)
{
this.amount = amount;
}
public void setUnitPrice(double unitPrice)
{
this.unitPrice = unitPrice;
}
public void setQuantity(int quantity)
{
this.quantity = quantity;
}
//toString method declaration
public String toString()
{
DecimalFormat pattern0dot00 = new DecimalFormat("$0.00");
return (((getQuantity() == 1) ? (getQuantity() + " order") : (getQuantity() + " orders")) + " of " +
getAmount() + " of " + getFlavor() + " ice cream in a " + getVessel() + " for " +
pattern0dot00.format(price()) + " = " + getQuantity() + " x " + getUnitPrice());
}
public static void main(String[] args)
{
//Object declarations
IceCreamOrder newOrder = new IceCreamOrder();
Scanner keyboard = new Scanner(System.in);
//Array declarations
String[] flavorList = {"Avocado", "Banana", "Chocolate", "Hazelnut", "Lemon", "Mango", "Mocha", "Vanilla"};
String[] vesselList = {"Cone", "Cup", "Sundae"};
String[] amountList = {"Single Scoop", "Double Scoop", "Triple Scoop"};
String[] quantityList = {"One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten"};
System.out.println("Placing an order is as easy as ABC, and D.");
System.out.println("Step A: Select your favorite flavour");
String outputFlavor = "";
for (int i = 1; i <= flavorList.length; i++)
{
outputFlavor = " (" + i + ") " + flavorList[i-1];
System.out.println(outputFlavor);
}
System.out.print("?-> Enter an option number: ");
int inputFlavor = keyboard.nextInt();
String flavorString = "";
switch (inputFlavor)
{
case 1:
flavorString = flavorList[0];
break;
case 2:
flavorString = flavorList[1];
break;
case 3:
flavorString = flavorList[2];
break;
case 4:
flavorString = flavorList[3];
break;
case 5:
flavorString = flavorList[4];
break;
case 6:
flavorString = flavorList[5];
break;
case 7:
flavorString = flavorList[6];
break;
case 8:
flavorString = flavorList[7];
break;
}
newOrder.setFlavor(flavorString);
System.out.println();
System.out.println("Step B: Select a vessel for your ice cream:");
String outputVessel = "";
for (int i = 1; i <= vesselList.length; i++)
{
outputVessel = " (" + i + ") " + vesselList[i-1];
System.out.println(outputVessel);
}
System.out.print("?-> Enter an option number: ");
int inputVessel = keyboard.nextInt();
String vesselString = "";
switch (inputVessel)
{
case 1:
vesselString = vesselList[0];
break;
case 2:
vesselString = vesselList[1];
break;
case 3:
vesselString = vesselList[2];
break;
}
newOrder.setVessel(vesselString);
System.out.println();
System.out.println("Step C: How much ice cream?");
String outputAmount = "";
for (int i = 1; i <= amountList.length; i++)
{
outputAmount = " (" + i + ") " + amountList[i-1];
System.out.println(outputAmount);
}
System.out.print("?-> Enter an option number: ");
int inputAmount = keyboard.nextInt();
String amountString = "";
switch (inputAmount)
{
case 1:
amountString = amountList[0];
break;
case 2:
amountString = amountList[1];
break;
case 3:
amountString = amountList[2];
break;
}
newOrder.setAmount(amountString);
System.out.println();
System.out.println("Step D: How many orders of your current selection?");
String outputQuantity = "";
for (int i = 1; i <= quantityList.length; i++)
{
outputQuantity = " (" + i + ") " + quantityList[i-1];
System.out.println(outputQuantity);
}
System.out.print("?-> Enter how many orders: ");
int inputQuantity = keyboard.nextInt();
newOrder.setQuantity(inputQuantity);
System.out.println();
if (newOrder.getAmount() == amountList[0])
{
if (newOrder.getVessel() == vesselList[0])
{
newOrder.setUnitPrice(2.99);
}
else if (newOrder.getVessel() == vesselList[1])
{
newOrder.setUnitPrice(3.49);
}
else
{
newOrder.setUnitPrice(4.25);
}
}
else if (newOrder.getAmount() == amountList[1])
{
if (newOrder.getVessel() == vesselList[0])
{
newOrder.setUnitPrice(3.99);
}
else if (newOrder.getVessel() == vesselList[1])
{
newOrder.setUnitPrice(4.49);
}
else
{
newOrder.setUnitPrice(5.25);
}
}
else
{
if (newOrder.getVessel() == vesselList[0])
{
newOrder.setUnitPrice(4.99);
}
else if (newOrder.getVessel() == vesselList[1])
{
newOrder.setUnitPrice(5.49);
}
else
{
newOrder.setUnitPrice(6.25);
}
}
System.out.println(newOrder);
}
}
这是我的ShoppingCart课程：
public class ShoppingCart
{
private IceCreamOrder[] shoppingCart;
private int maxQuantity;
private int orderTracker;
//Constructor declarations
public ShoppingCart()
{
this.shoppingCart = new IceCreamOrder[maxQuantity];
this.maxQuantity = 5;
this.orderTracker = 1;
}
public void add(IceCreamOrder order)
{
if (orderTracker > maxQuantity)
{
System.out.println("Shopping cart is full.");
}
else
{
shoppingCart[orderTracker - 1] = order;
orderTracker++;
}
}
//Method determines if shopping cart is empty
public boolean isEmpty()
{
int orderCount = 0;
for (int i = 0; i < shoppingCart.length; i++)
{
if (shoppingCart[i] != null)
{
orderCount++;
}
}
return ((orderCount == 0) ? true : false);
}
//Method determines if shopping cart is full
public boolean isFull()
{
int orderCount = 0;
for (int i = 0; i < shoppingCart.length; i++)
{
if (shoppingCart[i] != null)
{
orderCount++;
}
}
return ((orderCount == maxQuantity) ? true : false);
}
public IceCreamOrder get(int position)
{
return shoppingCart[position-1];
}
//Method determines the number of orders currently in shopping cart
public int size()
{
int orderCount = 0;
for (int i = 0; i < shoppingCart.length; i++)
{
if (shoppingCart[i] != null)
{
orderCount++;
}
}
return orderCount;
}
public static void main(String[] args)
{
ShoppingCart newCart = new ShoppingCart();
IceCreamOrder firstOrder = new IceCreamOrder("Vanilla", "Cone", "Single Scoop", 2.99);
IceCreamOrder secondOrder = new IceCreamOrder("Vanilla", "Cone", "Single Scoop", 2.99);
IceCreamOrder thirdOrder = new IceCreamOrder("Vanilla", "Cone", "Single Scoop", 2.99);
IceCreamOrder fourthOrder = new IceCreamOrder("Vanilla", "Cone", "Single Scoop", 2.99);
IceCreamOrder fifthOrder = new IceCreamOrder("Vanilla", "Cone", "Single Scoop", 2.99);
//IceCreamOrder sixthOrder = new IceCreamOrder("Vanilla", "Cone", "Single Scoop", 2.99);
newCart.add(firstOrder);
newCart.add(secondOrder);
newCart.add(thirdOrder);
newCart.add(fourthOrder);
newCart.add(fifthOrder);
//newCart.add(sixthOrder);*/
System.out.println(newCart.size());
System.out.println(firstOrder);
System.out.println(newCart.isEmpty());
System.out.println(newCart.isFull());
}
}