我之前在这里发布了关于这个项目的问题，这个问题在这里得到了很好的社区的回答。我正在创建一个自动售货机，它可以读取文本文件，在文本文件中创建一系列项目并将它们打印给用户，然后用户自行选择。我遇到了另一个障碍。
所以我的程序在日食中工作得很好，我遇到了零问题，并且我已经处理了我能想到的大多数异常。
当我通过我的课程成绩检查程序运行我的程序时，问题出现了，该程序将我的程序与预期的输出进行比较。换句话说，它显示了程序应该如何运行以及运行时应该返回什么值。
现在程序没有打印出与预期相同的值，我认为这会导致FileNotFoundException，因为我没有上传文本文件，所以一方面让我感到困惑。当需要从机器中选择一个项目时，我得到一个NoSuchElementException。我不知道为什么它会在检查器中执行此操作但在Eclipse中正常工作。非常感谢任何见解。
VendingMachine.java
import java.io.*;
import java.util.*;
import java.text.NumberFormat;
/*************************************************************************
* Simulates a real life vending machine with stock read from a file.
*
* CSCE 155A Spring 2016
* Assignment 4
* @file VendingMachine.java
* @author Jeremy Suing
* @version 1.0
* @date March 7, 2016
*************************************************************************/
public class VendingMachine {
//data members
private Item[] stock; //Array of Item objects in machine
private double money; //Amount of revenue earned by machine
/*********************************************************************
* This is the constructor of the VendingMachine class that take a
* file name for the items to be loaded into the vending machine.
*
* It creates objects of the Item class from the information in the
* file to populate into the stock of the vending machine. It does
* this by looping the file to determine the number of items and then
* reading the items and populating the array of stock.
*
* @param filename Name of the file containing the items to stock into
* this instance of the vending machine.
* @throws FileNotFoundException If issues reading the file.
*********************************************************************/
public VendingMachine(String filename) throws FileNotFoundException{
//Open the file to read with the scanner
File file = new File(filename);
Scanner scan = new Scanner(file);
//Determine the total number of items listed in the file
int totalItem = 0;
while (scan.hasNextLine()){
scan.nextLine();
totalItem++;
} //End while another item in file
//Create the array of stock with the appropriate number of items
stock = new Item[totalItem];
scan.close();
//Open the file again with a new scanner to read the items
scan = new Scanner(file);
int itemQuantity = -1;
double itemPrice = -1;
String itemDesc = "";
int count = 0;
String line = "";
//Read through the items in the file to get their information
//Create the item objects and put them into the array of stock
while(scan.hasNextLine()){
line = scan.nextLine();
String[] tokens = line.split(",");
try {
itemDesc = tokens[0];
itemPrice = Double.parseDouble(tokens[1]);
itemQuantity = Integer.parseInt(tokens[2]);
stock[count] = new Item(itemDesc, itemPrice, itemQuantity);
count++;
} catch (NumberFormatException nfe) {
System.out.println("Bad item in file " + filename +
" on row " + (count+1) + ".");
}
} //End while another item in file
scan.close();
//Initialize the money data variable.
money = 0.00;
} //End VendingMachine constructor
//To run the successful transaction
public void vend(double userInput, String userInput2) {
NumberFormat d = NumberFormat.getCurrencyInstance();
Scanner input = new Scanner(System.in);
boolean a = false;
boolean b = false;
String item = new String(userInput2);
double userMoney = userInput;
int errorNum = 0;
double addMoney = 0;
int itemSelect = 0;
if (userMoney==-4){
//errorNum=-4;
//this.outputMessage(userInput, errorNum);
a = true;
b=true;
}
while(!a){
b=false;
System.out.println("You now have " + d.format(userMoney) + " to spend. Please make a selection (enter 0 to exit): ");
item = input.next();
do{
try{
itemSelect = Integer.parseInt(item);
} catch (InputMismatchException e){
System.out.println("Invalid Entry!");
System.out.println("You now have " + d.format(userInput) + " to spend. Please make a selection (enter 0 to exit): ");
}
}while(!checkNum(item));
while(!b){
if(itemSelect==0){
System.out.println("You did not buy anything from this vending machine. Your change is " + d.format(userMoney));
b=true;
a=true;
} else if ((userMoney-stock[itemSelect-1].itemPrice)<0.00){
errorNum=-1;
this.outputMessage(userMoney, errorNum);
addMoney = input.nextDouble();
if (addMoney==-1){
errorNum = -3;
this.outputMessage(userMoney, errorNum);
b=true;
a=true;
}
userMoney = userMoney + addMoney;
b=true;
} else if (stock[itemSelect-1].itemQuantity==0){
errorNum = -2;
this.outputMessage(userMoney, errorNum);
b=true;
} else {
userMoney = userMoney-stock[itemSelect-1].itemPrice;
money = (money + stock[itemSelect-1].itemPrice);
this.outputMessage(userMoney, itemSelect);
stock[itemSelect-1].itemQuantity = stock[itemSelect-1].itemQuantity - 1;
b=true;
a=true;
}
}
}
}
//To determine whether or not the transaction was successful
public void outputMessage(double userInput, int userInput2) {
NumberFormat d = NumberFormat.getCurrencyInstance();
if(userInput2==-1){
System.out.println("You do not have enough money. Please add more money or exit.");
System.out.println("Please enter some money into the machine (enter -1 to exit): ");
} else if (userInput2==-2) {
System.out.println("Sorry, we are out of this item.");
} else if (userInput2==-3) {
System.out.println("You are exiting the vending machine. Your change is " + d.format(userInput));
} else {
System.out.println("You have purchased " + stock[userInput2-1].itemDesc + " for " + d.format(stock[userInput2-1].itemPrice) + ". Your change is " + d.format(userInput) + ".");
}
}
//To print the items in held in stock
public void printMenu() {
System.out.println("Item#" + "\t" + "Item" + "\t " + "Price" + "\t " + "Qty");
for(int i=0; i<stock.length;i++){
System.out.println( (i+1) + "\t" + stock[i]);
}
}
public static boolean checkNum(String userInput) {
try {
Integer.parseInt(userInput);
return true;
} catch (NumberFormatException e) {
return false;
}
}
public double getMoney() {
return money;
}
} //End VendingMachine class definition
Item.java
import java.util.*;
import java.text.NumberFormat;
public class Item {
String itemDesc;
double itemPrice;
int itemQuantity;
public Item (String itemDesc, double itemPrice, int itemQuantity){
this.itemDesc = itemDesc;
this.itemPrice = itemPrice;
this.itemQuantity = itemQuantity;
}
public String toString(){
NumberFormat d = NumberFormat.getCurrencyInstance();
return itemDesc + "\t" + " " + d.format(itemPrice) + "\t" + " " + itemQuantity + "\t";
}
}
VendingMachineDriver.java
import java.util.*;
import java.io.*;
import java.text.NumberFormat;
public class VendingMachineDriver {
public static void main(String args[]) throws FileNotFoundException {
Scanner input = new Scanner(System.in);
//String vendingSelect = input.next();
String a = new String("a");
String b = new String("b");
String x = new String("x");
String item = "0";
boolean exit = false;
VendingMachine drinks = new VendingMachine("drinks");
VendingMachine snacks = new VendingMachine("snacks");
NumberFormat d = NumberFormat.getCurrencyInstance();
while(!exit){
boolean c = false;
System.out.println("Welcome to Jeremy's Super Vending Machines!");
System.out.println("Please select a vending machine:");
System.out.println("A-Drinks, B-Snacks, X-Exit");
String vendingSelect = input.next();
while(!c){
if(a.equalsIgnoreCase(vendingSelect)){
drinks.printMenu();
System.out.println("Please enter some money into the machine (enter -1 to exit)");
double money = input.nextDouble();
if (money==-1){
System.out.println("You did not buy anything from this vending machine. Your change is " + d.format(0) + "." );
c = true;
} else {
System.out.println("You now have " + d.format(money) + " to spend. Please make a selection (enter 0 to exit): ");
item = input.next();
drinks.vend(money, item);
c=true;
}
}
else if(b.equalsIgnoreCase(vendingSelect)){
snacks.printMenu();
System.out.println("Please enter some money into the machine (enter -1 to exit)");
double money = input.nextDouble();
if (money==-1){
System.out.println("You did not buy anything from this vending machine. Your change is " + d.format(0) + "." );
c = true;
}
else {
System.out.println("You now have " + d.format(money) + " to spend. Please make a selection (enter 0 to exit): ");
item = input.next();
snacks.vend(money, item);
c=true;
}
} else if(x.equalsIgnoreCase(vendingSelect)){
double errorNum = -4;
snacks.vend(errorNum, item);
System.out.println("The vending machines made a total of " + d.format(drinks.getMoney()) + "." );
System.out.println("Thank you for your business!");
c=true;
exit=true;
}
}
}
}
}
答案 0 :(得分：1)
public class NoSuchElementException
extends RuntimeException
由枚举的nextElement方法抛出，表示枚举中没有更多元素。
在您的驱动程序类中，您正在调用input.next();或input.nextDouble();或其他任何内容，而无需测试您是否确实要获取下一个元素。您需要以某种方式合并if ( input.hasNext() )或while (input.hasNext())以防止此类错误。