问题：
输入文件：客户的帐号，帐号余额为 月初，交易类型（提款，存款， 利息），交易金额
输出帐号，期初余额，期末余额， 支付的利息总额，存款总额，数量 存款，提取的总金额，提款数量
package sentinel;
import java.io.*;
import java.util.*;
public class Ex7 {
/**
* @param args the command line arguments
*/
public static void main(String[] args) throws FileNotFoundException
{
int AccountNum;
double BeginningBalance;
double TransactionAmount;
int TransactionType;
double AmountDeposited=0;
int NumberOfDeposits=0;
double InterestPaid=0.0;
double AmountWithdrawn=0.0;
int NumberOfWithdrawals=0;
boolean found= false;
Scanner inFile = new Scanner(new FileReader("Account.in"));
PrintWriter outFile = new PrintWriter("Account.out");
AccountNum = inFile.nextInt();
BeginningBalance= inFile.nextDouble();
while (inFile.hasNext())
{
TransactionAmount=inFile.nextDouble();
TransactionType=inFile.nextInt();
outFile.printf("Account Number: %d%n", AccountNum);
outFile.printf("Beginning Balance: $%.2f %n",BeginningBalance);
outFile.printf("Ending Balance: $%.2f %n",BeginningBalance);
outFile.println();
switch (TransactionType)
{
case '1': // case 1 if we have a Deposite
BeginningBalance = BeginningBalance
+ TransactionAmount;
AmountDeposited = AmountDeposited
+ TransactionAmount;
NumberOfDeposits++;
outFile.printf("Amount Deposited: $%.2f %n",AmountDeposited);
outFile.printf("Number of Deposits: %d%n",NumberOfDeposits);
outFile.println();
break;
case '2':// case 2 if we have an Interest
BeginningBalance = BeginningBalance
+ TransactionAmount;
InterestPaid = InterestPaid
+ TransactionAmount;
outFile.printf("Interest Paid: $%.2f %n",InterestPaid);
outFile.println();
break;
case '3':// case 3 if we have a Withdraw
BeginningBalance = BeginningBalance
- TransactionAmount;
AmountWithdrawn = AmountWithdrawn
+ TransactionAmount;
NumberOfWithdrawals++;
outFile.printf("Amount Withdrawn: $%.2f %n",AmountWithdrawn);
outFile.printf("Number of Withdrawals: %d%n",NumberOfWithdrawals);
outFile.println();
break;
default:
System.out.println("Invalid transaction Tybe: " + TransactionType
+ TransactionAmount);
}
}
inFile.close();
outFile.close();
}
}
但是给了我这个：
Exception in thread "main" java.util.InputMismatchException
at java.util.Scanner.throwFor(Scanner.java:840)
at java.util.Scanner.next(Scanner.java:1461)
at java.util.Scanner.nextInt(Scanner.java:2091)
at java.util.Scanner.nextInt(Scanner.java:2050)
at sentinel.Ex7.main(Ex7.java:36)
Java Result: 1
答案 0 :(得分：3)
这就是我要继续下去的方式：
您可能还不知道如何使用调试器，虽然有些人可能不同意，但我认为这永远不会太早。有一些关于如何使用调试器here的优秀视频教程。祝你好运！
答案 1 :(得分：2)
我想回答这个问题有点太晚了，但我最近偶然发现了同样的问题，我的谷歌搜索引导我来到这里。
我认为InputMismatchException引发的Scanner.nextDouble()最常见的情况是Scanner使用的默认语言环境预计会以不同的格式加倍（例如10,5，不是10.5）。如果是这种情况，您应该使用Scanner.useLocale这样的方法
Scanner s = new Scanner(System.in);
s.useLocale(Locale.US);
答案 2 :(得分：1)
如果您阅读Exception条消息，则为InputMismatchException。这很可能是由nextDouble()或nextInt()函数引起的，当它没有读取正确的类型时。确保您的数据正确对齐，并且您没有使用readInt()读取双打。
答案 3 :(得分：1)
您可能希望包含Account.in的内容以提供更多信息，但以下是一些评论：
变量：除变量外，所有实例，类和类常量都是大小写混合，带有小写的第一个字母。
这意味着按照惯例，变量名称应该是大写/小写，如accountNum，beginningBalance，numberOfDeposits等。
还应该提到的是，放置花括号的方式非常不同寻常。 learn good coding style可能是个好主意。
这部分也非常不一致：
int TransactionType; // declared as int
//...
TransactionType=inFile.nextInt(); // read as int
//...
switch (TransactionType)
case '1': // used as ... char? ASCII '1' = 49
我99％确定您确实需要switch，case 1:，case 2:上的case 3:。
您可能还需要打印处理完交易的结束余额 AFTER 。现在，您将始终为开始和结束余额打印相同的数字。
知道Java具有“复合赋值”运算符可以使您的代码更具可读性，这也可能对您有所帮助。你可能现在不需要关心自己的确切语义，但基本上不是这样：
BeginningBalance = BeginningBalance
+ TransactionAmount;
BeginningBalance = BeginningBalance
- TransactionAmount;
你可以写：
beginningBalance += transactionAmount;
beginningBalance -= transactionAmount;
最后，关于InputMismatchException的最后一条评论：其他人已经向您解释了这意味着什么。我现在最好的猜测是你的问题是由此引起的：
输入文件：客户的帐号，月初的帐户余额，交易类型（提款，存款，利息），交易金额
VS
TransactionAmount=inFile.nextDouble();
TransactionType=inFile.nextInt();
我需要看Account.in确认，但我怀疑int交易类型出现在double交易金额之前，就像问题陈述所说的那样。您的代码以相反的顺序读取它们。
这会尝试将int读作nextDouble()，这是可以的，但double为nextInt()会抛出InputMismatchException。
答案 4 :(得分：1)
我并不特别喜欢这个设计，因为它违背了Java的优点，有点面向对象。所以我按照我的想法重写了这个程序。
我还发现解释双打是依赖于语言环境，在我的机器上，double（在一个字符串中）应该有一个逗号（12,12）而不是一个点（12.12），所以可能是你的问题。
正如polygenelubricants所说，成员和方法名称在Java中较低，只有类型使用大写。
我添加了我自己的实现，不是因为你的工作不起作用，而是为了展示如何将责任委托给反映问题域的类，使代码更具可读性（尽管使用样板读取器和设置器的时间要长得多）。
我的程序实现类似于：
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.PrintWriter;
import java.util.Scanner;
public class Ex7 {
/**
* One transaction record in the file Should be format "int double\n"
* Note that interpreting a double is locale dependent, on my machine
* I need "12,24" whereas a US locale might require "12.24"
*/
public static class Transaction {
double amount;
int type; // Prefer an enum here...
public void read(Scanner scanner) {
setAmount(scanner.nextDouble());
setType(scanner.nextInt());
}
public int getType() {
return type;
}
public void setType(int type) {
this.type = type;
}
public double getAmount() {
return amount;
}
public void setAmount(double amount) {
this.amount = amount;
}
@Override
public String toString() {
return String.format("Transaction(type=%d, amount=%.2f)", type, amount);
}
}
/**
* Account information and processing Account file format: Line 1
* "int double\n" account number start balance Line 2-... "double int\n"
* transaction amount transaction type.
* Type 1=deposit, 2=interest
* 3=withdrawal
*/
public static class Account {
int accountNum;
double startBalance;
double currentBalance;
double totalDeposited;
double totalWithdrawn;
double totalInterestPaid;
int numberOfDeposits;
int numberOfWithdrawals;
int numberOfInterestPayments;
public Account(Scanner scanner) {
read(scanner);
}
private void read(Scanner scanner) {
setAccountNum(scanner.nextInt());
setStartBalance(scanner.nextDouble());
setCurrentBalance(getStartBalance());
}
public int getAccountNum() {
return accountNum;
}
public void setAccountNum(int accountNum) {
this.accountNum = accountNum;
}
public double getStartBalance() {
return startBalance;
}
public void setStartBalance(double startBalance) {
this.startBalance = startBalance;
}
public double getCurrentBalance() {
return currentBalance;
}
public void setCurrentBalance(double currentBalance) {
this.currentBalance = currentBalance;
}
public void processTransaction(Transaction transaction) {
switch (transaction.getType()) {
case 1:
handleDeposit(transaction.getAmount());
break;
case 2: // Isn't this just a deposit?
handleInterest(transaction.getAmount());
break;
case 3:
handleWithdraw(transaction.getAmount());
break;
default:
throw new RuntimeException("Can not process transaction " + transaction + ", transaction type unknown.");
}
}
private void handleDeposit(double deposit) {
numberOfDeposits++;
currentBalance += deposit;
totalDeposited += deposit;
}
private void handleInterest(double interestPaid) {
numberOfInterestPayments++;
currentBalance += interestPaid;
totalInterestPaid += interestPaid;
}
private void handleWithdraw(double amountWithdrawn) {
numberOfWithdrawals++;
currentBalance -= amountWithdrawn;
totalWithdrawn += amountWithdrawn;
}
public String getOverview() {
StringBuilder stringBuilder = new StringBuilder();
stringBuilder.append("Total Deposited : " + totalDeposited).append("\n");
stringBuilder.append("Total Withdrawn : " + totalWithdrawn).append("\n");
stringBuilder.append("Total Interest : " + totalInterestPaid).append("\n");
stringBuilder.append("Current Balance : " + currentBalance).append("\n").append("\n");
return stringBuilder.toString();
}
}
/**
* @param args
* the command line arguments
*/
public static void main(String[] args) throws FileNotFoundException {
Scanner inFile = null;
PrintWriter outFile= null;
try {
inFile = new Scanner(new FileReader("Account.in"));
outFile = new PrintWriter("Account.out");
Account account;
try {
account = new Account(inFile);
} catch (RuntimeException e) {
// Catch exception for error message display
System.err.println("Could not read account information from file. Quitting");
System.exit(1);
return; // Otherwise compiler error :)
}
int lineNumber = 1; // Start with 1 because first line has account info
while (inFile.hasNext()) {
Transaction transaction = new Transaction();
try {
transaction.read(inFile);
} catch (RuntimeException e) {
System.err.println("An error ocurred while processing a transaction on line " + lineNumber + ". Transaction " + transaction + " incomplete and failed");
throw e; // rethrow and let the stack trace shine!
}
lineNumber++;
outFile.printf("Account Number: %d%n", account.getAccountNum());
outFile.printf("Beginning Balance: $%.2f %n", account.getStartBalance());
outFile.printf("Current Balance: $%.2f %n", account.getCurrentBalance());
outFile.println();
account.processTransaction(transaction);
outFile.print(account.getOverview());
}
} finally {
if (inFile != null) {
inFile.close(); // This can also yield an exception, but I just don't care anymore :)
}
if (outFile != null) {
outFile.close();
}
}
}
}