需要帮助一些有这个错误，我无法搞清楚。该程序假设读取输入并保存。线程“main”java.util.InputMismatchException中的异常 ÏϧÏ在java.util.Scanner.throwFor（Scanner.java:864） ÏϧÏ在java.util.Scanner.next（Scanner.java:1485） ÏϧÏ在java.util.Scanner.nextDouble（Scanner.java:2413） ÏϧÏ在Driver.main（Driver.java:112） ÏϧÏ
===================================
import java.io.*;
import java.util.Scanner;
public class Driver
{
public static void main(String[] args)
{
//local constants
//local variables
String fileName = "items.txt";
Scanner scanner = null;
ItemsList itemsList = new ItemsList(5);
int i = 0;
int choice;
boolean repeat = true;
String itemName;
double price;
int qty;
scanner=new Scanner(System.in);
//****************************************************************************
//open the file and catch the exception if file not found
try
{
//create an instance of scanner
scanner = new Scanner(new File(fileName));
//read file items until end of file
while(scanner.hasNext())
{
itemName = scanner.next();
price = scanner.nextDouble();
qty=scanner.nextInt();
//Add the OneItem object to the itemList
itemsList.addItem(new OneItem(itemName, price, qty));
i++;
}
//close the file object
scanner.close();
}
catch (FileNotFoundException e)
{
System.out.println(e.getMessage());
}
//Create an instance of Scanner class
scanner=new Scanner(System.in);
while(repeat)
{
//call menu
choice = menu();
switch(choice)
{
//Add an item to the itemsList
case 1:
System.out.println("Enter item name : ");
//read name
String name=scanner.nextLine();
System.out.println("Enter price : ");
//read string value and parse to double value
price = Double.parseDouble(scanner.nextLine());
System.out.println("Enter quantity : ");
qty=Integer.parseInt(scanner.nextLine());
//Add the OneItem to the itemsList
itemsList.addItem(new OneItem(name, price, qty));
break;
case 2:
//print the list
//print heading with specific formatter
System.out.printf("%-10s%-10s%-10s\n\n", "Item","Price","Quantity");
System.out.println(itemsList.toString());
break;
case 3:
//Terminate the program
System.out.println("Terminate the program.");
//set repeat to false
repeat=false;
break;
default:
System.out.println("Incorrect option is selected.");
break;
}
}
writeToFile(itemsList);
}
private static void writeToFile(ItemsList itemsList)
{
//Create a file name called items.txt
String filename="items.txt";
//Create a variable of Class PrintWriter
PrintWriter filewriter=null;
try
{
//create an instance of PrintWriter
filewriter=new PrintWriter(new File(filename));
//close the file writer
filewriter.close();
}
catch (IOException e)
{
System.out.println(e.getMessage());
}
}
private static int menu()
{
//Create an instance of Scanner class
Scanner keyboard=new Scanner(System.in);
System.out.println("Menu");
System.out.println("1. Add item");
System.out.println("2. Display items");
System.out.println("3. Exit");
System.out.println("Enter your choice");
int choice=Integer.parseInt(keyboard.nextLine());
return choice;
}
}//end Driver class
==========================================
public class OneItem
{
//declare a variables
private String name;
private double price;
private int quantity;
//default constructor
public OneItem()
{
name = "";
price = 0;
quantity = 0;
}
//parameter constructor
public OneItem(String name, double price, int quantity)
{
this.name = name;
this.price = price;
this.quantity = quantity;
}
//toString
public String toString()
{
return String.format("%-10s%-10.2f%-10d\n", name,price,quantity);
}
}//end of the OneItem class
===========================
public class ItemsList
{
//declare variables
private OneItem items[];
private int size;
private int count;
//constructor to set items, size and count to zero
public ItemsList()
{
items = null;
size = 0;
count = 0;
}
//Parameter constructor
public ItemsList(int size)
{
items = new OneItem[size];
for (int i = 0; i < items.length; i++)
{
items[i] = new OneItem();
}
this.size = size;
count = 0;
}
//Add OneItem to the itemlist
public void addItem(OneItem item)
{
if(items.length == count)
{
resize();
items[count] = item;
count++;
}
else
{
items[count] = item;
count++;
}
}
//Resize
private void resize()
{
int oldsize = size;
count = oldsize;
int newsize = 2 * this.size;
size = newsize;
OneItem[] tempList = new OneItem[size];
for (int i = 0; i < oldsize; i++)
tempList[i] = items[i];
items = new OneItem[size];
items = tempList;
}
//getSize
public int getSize()
{
return count;
}
//toString
public String toString()
{
String description = "";
for (int i = 0; i <count; i++)
{
description += items[i].toString();
}
return description;
}
}
答案 0 :(得分：0)
将来，您需要更清楚问题是什么。它是如何发生的。输入字符串到购买价格时得到的错误是：
Exception in thread "main" java.lang.NumberFormatException: For input string: "sdcf"
at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:2043)
at sun.misc.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
at java.lang.Double.parseDouble(Double.java:538)
at stacktests.Driver.main(Driver.java:70)
意味着您完全不验证您的输入。例如：
Scanner sc = new Scanner(System.in);
while (!sc.hasNextInt())
{
System.out.println("Enter an integer!");
sc.nextLine();
}
int num = sc.nextInt();
System.out.println("Thank you! (" + num + ")");
您需要禁止将字符串输入到数字变量中！只有在验证输入后，才将其分配给变量。
干杯队友。