我正在尝试编写一个简单的银行账户管理程序，该程序执行以下操作：
创建一个新帐户，其帐号和余额取自用户并存储在数组中 选择一个帐户（来自数组） 删除所选帐户 选择提款和存款。
问题：我不明白我的错误是什么。
我尝试使用不同类型的数组进行帐号和余额存储，但我还没有找到答案。我搜索Web和Stackoverflow以获取参考，文档，简单示例，但找不到任何（我发现的那些，使用了一些我还没有学过的命令和东西，所以我可以理解它们是如何工作的）。我是初学者，我还在学习，并希望得到一些建议。谢谢！
//Bank account class
public class account {
private int ANumber;
private double balance;
public account(double initialBalance, int accno) {
balance = initialBalance;
ANumber = accno;
}
public void deposit (double u_amm){
balance += u_amm;
}
public double withdraw(double amount) {
balance -= amount;
return amount;
}
public double getBalance() {
return balance;
}
public int getAccount(){
return ANumber;
}
}
这是主类
import java.util.Scanner;
// main class
public class bankmain {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
// Menu starts from here
Scanner input = new Scanner(System.in);
System.out.println("Enter the option for the operation you need:");
System.out.println("****************************************************");
System.out.println("[ Options: ne - New Account de - Delete Account ]");
System.out.println("[ dp - Deposit wi - Withdraw ]");
System.out.println("[ se - Select Account ex - Quit ]");
System.out.println("****************************************************");
System.out.print("> "); //indicator for user input
String choice = input.next();
//Options
while(true){
if(choice == "ne"){
int nacc;
int bal;
int [][]array = new int[nacc][bal]; // Array for account and balance
System.out.print("Insert account number: ");
nacc =input.nextInt(); //-- Input nr for array insertion
System.out.print("Enter initial balance: ");
bal=input.nextInt(); //-- Input nr for array insertion
System.out.println("Current account: " + nacc + " " + "Balance " + bal);
break;
}
// account selection
if(choice.equals("se")){
System.out.println("Enter number of account to be selected: ");
//user input for account nr from array
System.out.println("Account closed.");
}
//close account
if(choice.equals("de")){
//array selected for closing
System.out.println("Account closed.");
}
// deposit
if(choice.equals("dp")){
System.out.print("Enter amount to deposit: ");
double amount = scan.nextDouble();
if(amount <= 0){
System.out.println("You must deposit an amount greater than 0.");
} else {
System.out.println("You have deposited " + (amount + account.getBalance()));
}
}
// withdrawal
if(choice.equals("wi")){
System.out.print("Enter amount to be withdrawn: ");
double amount = scan.nextDouble();
if (amount > account.balance()){
System.out.println("You can't withdraw that amount!");
} else if (amount <= account.balance()) {
account.withdraw(amount);
System.out.println("NewBalance = " + account.getBalance());
}
}
//quit
if(choice == "ex"){
System.exit(0);
}
} // end of menu loop
}// end of main
} // end of class
答案 0 :(得分：2)
您的代码在许多级别上都是错误的 - 首先尝试处理您的格式和命名约定，这样您就不会学习糟糕的习惯。不要使用小的leters来命名类，尝试使用完整的单词来描述变量和字段，就像在Account.class示例中一样：
public class Account {
private Integer accountNumber;
private Double balance;
public Account(final Integer accountNumber, final Double initialBalance) {
this.accountNumber = accountNumber;
balance = initialBalance;
}
public Double deposit (double depositAmmount) {
balance += depositAmmount;
return balance;
}
public Double withdraw(double withdrawAmmount) {
balance -= withdrawAmmount;
return balance;
}
public Double getBalance() {
return balance;
}
public Integer getAccountNumber() {
return accountNumber;
}
}
还尝试在所有代码中使用相同的格式（即括号后的空格），以便您阅读起来更简单。
现在 - 您的应用中出现了什么问题：
为您的帐户定义合适的持有人，即HashMap，其中包含有关所有帐户的信息，并且可以通过accountNumber找到它们。
HashMap<Integer, Account> accountMap = new HashMap<Integer, Account>();
这个应该在你的while循环中，因为你希望你的用户做多个任务。您可以省略println，但用户必须返回到屏幕顶部才能看到选项。
System.out.println("Enter the option for the operation you need:");
System.out.println("****************************************************");
System.out.println("[ Options: ne - New Account de - Delete Account ]");
System.out.println("[ dp - Deposit wi - Withdraw ]");
System.out.println("[ se - Select Account ex - Quit ]");
System.out.println("****************************************************");
System.out.print("> "); //indicator for user input
String choice = input.nextLine();
System.out.println("Your choice: " + choice);
您不应该使用＆＃39; ==＆＃39;来比较字符串。运营商，因为它可能不会返回预期值。请查看：How do I compare strings in Java?或What is the difference between == vs equals() in Java?。对于安全使用，对象等于，即：
choice.equals("ne")
您没有创建帐户的地方：
Account newAccount = new Account(newAccountNumber, initialBalance);
你没有使用if-else，只是如果有的话。它应该看起来更像（为什么要检查选择是否＆＃39;如果它已被发现是＆＃39; ne＆＃39;）
if(choice.equals("ne")) {
//doStuff
} else if choice.equals("se") {
//doStuff
} //and so on.
如果您使用的是Java版本＆gt; = 7，那么您可以使用开关来比较字符串而不是if-else。
没有错误选项的通知：
} else {
System.out.println("Wrong option chosen.");
}
您没有关闭Scanner对象。这在这里并不重要，因为它在主要方法中并且将与它关闭，但是在使用它时总是关闭你的流，数据源等是很好的习惯问题：< / p>
input.close();
所以整个代码看起来像这样：
import java.util.HashMap;
import java.util.Scanner;
// main class
public class BankAccount {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
HashMap<Integer, Account> accountMap = new HashMap<Integer, Account>();
//Options
while(true) {
System.out.println("Enter the option for the operation you need:");
System.out.println("****************************************************");
System.out.println("[ Options: ne - New Account de - Delete Account ]");
System.out.println("[ dp - Deposit wi - Withdraw ]");
System.out.println("[ se - Select Account ex - Quit ]");
System.out.println("****************************************************");
System.out.print("> "); //indicator for user input
String choice = input.next();
System.out.println("Your choice: " + choice);
if(choice.equals("ne")) {
Integer newAccountNumber;
Double initialBalance;
Account newAccount;
// Array for account and balance
System.out.print("Insert account number: ");
newAccountNumber = input.nextInt(); //-- Input nr for array insertion
System.out.print("Enter initial balance: ");
initialBalance=input.nextDouble(); //-- Input nr for array insertion
newAccount = new Account(newAccountNumber, initialBalance);
accountMap.put(newAccountNumber, newAccount);
System.out.println("New Account " + newAccountNumber + " created with balance: " + initialBalance);
}
//select account
else if(choice.equals("se")) {
System.out.println("Enter number of account to be selected: ");
Integer accountToGetNumber = input.nextInt();
Account returnedAccount = accountMap.get(accountToGetNumber);
if (returnedAccount != null)
{
System.out.println("Account open. Current balance: " + returnedAccount.getBalance());
}
else
{
//user input for account nr from array
System.out.println("Account does not exist.");
}
}
//close account
else if(choice.equals("de"))
{
System.out.println("Enter number of account to be selected: ");
Integer accountToDeleteNumber = input.nextInt();
Account removedAccount = accountMap.remove(accountToDeleteNumber);
if (removedAccount != null)
{
System.out.println("Account " + removedAccount.getAccountNumber() + " has been closed with balance: " + removedAccount.getBalance());
}
else
{
//user input for account nr from array
System.out.println("Account does not exist.");
}
}
// deposit
else if(choice.equals("dp")) {
System.out.println("Enter number of account to deposit: ");
Integer accountToDeposit = input.nextInt();
System.out.print("Enter amount to deposit: ");
double amount = input.nextDouble();
if(amount <= 0){
System.out.println("You must deposit an amount greater than 0.");
} else {
accountMap.get(accountToDeposit).deposit(amount);
System.out.println("You have deposited " + (amount));
System.out.println("Current balance " + accountMap.get(accountToDeposit).getBalance());
}
}
// withdrawal
else if(choice.equals("wi")) {
System.out.println("Enter number of account to withdraw: ");
Integer accountToWithdraw = input.nextInt();
System.out.print("Enter amount to withdraw: ");
double amount = input.nextDouble();
if(amount <= 0) {
System.out.println("You must deposit an amount greater than 0.");
} else {
accountMap.get(accountToWithdraw).withdraw(amount);
System.out.println("You have deposited " + (amount));
System.out.println("Current balance " + accountMap.get(accountToWithdraw).getBalance());
}
}
//quit
else if(choice.equals("ex")) {
break;
} else {
System.out.println("Wrong option.");
} //end of if
} //end of loop
input.close();
} //end of main
} //end of class
还有很多需要改进的地方，即输入验证 - 但这应该适用于开始。
答案 1 :(得分：1)
您已经编写了上述代码，但它有很多错误。您需要了解The basics of Java programming。
我修改了您的程序以执行以下操作： -
Account.java：
/**
* This class performs bank operations
*/
public class Account {
private int accNumber;
private double balance;
public Account(double initialBalance, int accNo) {
balance = initialBalance;
accNumber = accNo;
}
public void deposit(double amount) {
balance += amount;
}
public double withdraw(double amount) {
balance -= amount;
return amount;
}
public double getBalance() {
return balance;
}
public int getAccNumber() {
return accNumber;
}
}
BankMain.java：
public class BankMain {
private static double amount;
private static ArrayList<Account> accountList = new ArrayList<>();
private static Account selectedAccount;
private static boolean flag = false;
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
// Menu starts from here
Scanner input = new Scanner(System.in);
System.out.println("Enter the option for the operation you need:");
System.out
.println("****************************************************");
System.out
.println("[ Options: new - New Account del - Delete Account ]");
System.out
.println("[ dp - Deposit wi - Withdraw bal - Check balance ]");
System.out
.println("[ se - Select Account exit - Quit ]");
System.out
.println("****************************************************");
Account account = null;
while (true) {
System.out.println("> "); // indicator for user input
String choice = input.next();
// Options
switch (choice) {
case "new":
// Create new account
int accNo = 0;
int bal = 0;
System.out.println("Enter account number : ");
accNo = input.nextInt();
System.out.println("Enter initial balance: ");
bal = input.nextInt();
System.out.println("Current account: " + accNo + " "
+ "Balance " + bal);
account = new Account(bal, accNo);
accountList.add(account);
break;
case "se":
// select account
System.out
.println("Enter account number for further operations : ");
int selectedAcc = scan.nextInt();
System.out.println("Selected account : " + selectedAcc);
for (Object object : accountList) {
selectedAccount = (Account) object;
if (selectedAccount.getAccNumber() == selectedAcc) {
flag = true;
break;
} else {
flag = false;
}
}
if (!flag) {
System.out.println("Account doesn't exists.");
}
if (accountList.size() == 0) {
System.out.println("Zero account exists.");
}
break;
case "del":
// close account
System.out
.println("Enter account number for further operations : ");
int selectedAcc1 = scan.nextInt();
System.out.println("Selected account : " + selectedAcc1);
Iterator<Account> iterator = accountList.iterator();
while (iterator.hasNext()) {
selectedAccount = (Account) iterator.next();
if (selectedAccount.getAccNumber() == selectedAcc1) {
iterator.remove();
flag = true;
break;
}
}
if (!flag) {
System.out.println("Account doesn't exists.");
}
System.out.println("Account " + selectedAcc1 + " closed.");
break;
case "dp":
// Deposit amount
System.out.println("Enter amount to deposit : ");
amount = scan.nextDouble();
if (amount <= 0) {
System.out
.println("You must deposit an amount greater than 0.");
} else {
if (flag) {
selectedAccount.deposit(amount);
System.out.println("You have deposited " + amount
+ ". Total balance : "
+ (selectedAccount.getBalance()));
} else {
System.out.println("Please select account number.");
}
}
break;
case "wi":
// Withdraw amount
System.out.println("Enter amount to be withdrawn: ");
amount = scan.nextDouble();
if (amount > account.getBalance() && amount <= 0) {
System.out.println("You can't withdraw that amount!");
} else if (amount <= selectedAccount.getBalance()) {
if (flag) {
selectedAccount.withdraw(amount);
System.out.println("You have withdraw : " + amount
+ " NewBalance : "
+ selectedAccount.getBalance());
} else {
System.out.println("Please select account number.");
}
}
break;
case "bal":
// check balance in selected account
if (flag) {
System.out.println("Your current account balance : "
+ selectedAccount.getBalance());
} else {
System.out.println("Please select account number.");
}
break;
case "exit":
default:
// quit
System.out.println("Thank You. Visit Again!");
flag = false;
input.close();
scan.close();
System.exit(0);
break;
}
} // end of menu loop
}// end of main
} // end of class
我已经测试了这个代码＆amp;它工作正常。
输出
Enter the option for the operation you need:
****************************************************
[ Options: new - New Account del - Delete Account ]
[ dp - Deposit wi - Withdraw bal - Check balance ]
[ se - Select Account exit - Quit ]
****************************************************
> new
Enter account number : 101
Enter initial balance: 10000
Current account: 101 Balance 10000
> new
Enter account number : 102
Enter initial balance: 25000
Current account: 102 Balance 25000
> se
Enter account number for further operations : 103
Selected account : 103
Account doesn't exists.
> se
Enter account number for further operations : 101
Selected account : 101
> bal
Your current account balance : 10000.0
> dp
Enter amount to deposit : 2500
You have deposited 2500.0. Total balance : 12500.0
> wi
Enter amount to be withdrawn: 500
You have withdraw : 500.0 NewBalance : 12000.0
> se
Enter account number for further operations : 102
Selected account : 102
> bal
Your current account balance : 25000.0
> del
Enter account number for further operations : 101
Selected account : 101
Account 101 closed.
> se
Enter account number for further operations : 101
Selected account : 101
Account doesn't exists.
> exit
Thank You. Visit Again!