Java 创建银行计划

我几乎完成了一项任务。我正在创建一个银行项目，我几乎完成了所有的事情。我一直坚持的部分是交易部分。我必须创建一个函数

public String getTransactionInfo（int n）

，它返回银行帐户的最后n笔交易。我似乎无法理解这一部分。我有一个变量

private int numOfTransactions

，我尝试将它合并到函数中，但没有成功。这就是我试过的

public String gettransactionInfo(int n)
{
    numOfTransactions = n;
    return n;
}

那是行不通的。无法确定如何返回这是一个字符串。有什么想法吗

import java.util.Scanner;
public class BankApp {
public static void main(String[] args) {
    Scanner s = new Scanner(System.in);
    Bank myBank = new Bank();

    int user_choice = 2;

    do {
        //display menu to user
        //ask user for his choice and validate it (make sure it is between 1 and 6)
        System.out.println();
        System.out.println("1) Open a new bank account");
        System.out.println("2) Deposit to a bank account");
        System.out.println("3) Withdraw to bank account");
        System.out.println("4) Print short account information");
        System.out.println("5) Print the detailed account information including last transactions");
        System.out.println("6) Quit");
        System.out.println();
        System.out.print("Enter choice [1-6]: ");
        user_choice = s.nextInt();
        switch (user_choice) {
            case 1: System.out.println("Enter a customer name");
                    String cn = s.next();
                    System.out.println("Enter a opening balance");
                    double d = s.nextDouble();
                    System.out.println("Account was created and it has the following number: " + myBank.openNewAccount(cn, d));
                    break;
            case 2: System.out.println("Enter a account number");
                    int an = s.nextInt();
                    System.out.println("Enter a deposit amount");
                    double da = s.nextDouble();
                    myBank.depositTo(an, da);
                    break;
            case 3: System.out.println("Enter a account number");
                    int acn = s.nextInt();
                    System.out.println("Enter a withdraw amount");
                    double wa = s.nextDouble();
                    myBank.withdrawFrom(acn, wa);
                    break;
            case 4: System.out.println("Enter a account number");
                    int anum = s.nextInt();
                    myBank.printAccountInfo(anum);
                    break;
            //case 5: ... break;
        }
}
while (user_choice != '6');
}

static class Bank {
private BankAccount[] accounts;     // all the bank accounts at this bank
private int numOfAccounts;      // the number of bank accounts at this bank

// Constructor: A new Bank object initially doesn’t contain any accounts.
public Bank() {
    accounts = new BankAccount[100];
    numOfAccounts = 0;
    }

// Creates a new bank account using the customer name and the opening balance given as parameters
// and returns the account number of this new account. It also adds this account into the account list
// of the Bank calling object.
public int openNewAccount(String customerName, double openingBalance) {

    BankAccount b = new BankAccount(customerName, openingBalance);
    accounts[numOfAccounts] = b;
    numOfAccounts++;
    return b.getAccountNum();
}

// Withdraws the given amount from the account whose account number is given. If the account is
// not available at the bank, it should print a message.
public void withdrawFrom(int accountNum, double amount) {
    for (int i =0; i<numOfAccounts; i++) {
        if (accountNum == accounts[i].getAccountNum()  ) {
            accounts[i].withdraw(amount);
            System.out.println("Amount withdrawn successfully");
            return;
        }
    }
    System.out.println("Account number not found.");
    }

// Deposits the given amount to the account whose account number is given. If the account is not
// available at the bank, it should print a message.
public void depositTo(int accountNum, double amount) {
    for (int i =0; i<numOfAccounts; i++) {
        if (accountNum == accounts[i].getAccountNum()  ) {
            accounts[i].deposit(amount);
            System.out.println("Amount deposited successfully");
            return;
        }
    }
    System.out.println("Account number not found.");
}

// Prints the account number, the customer name and the balance of the bank account whose
// account number is given. If the account is not available at the bank, it should print a message.
public void printAccountInfo(int accountNum) {
    for (int i =0; i<numOfAccounts; i++) {
                if (accountNum == accounts[i].getAccountNum()  ) {
                    System.out.println(accounts[i].getAccountInfo());
                    return;
                }
            }
    System.out.println("Account number not found.");
}

// Prints the account number, the customer number and the balance of the bank account whose
// account number is given, together with last n transactions on that account. If the account is not
// available at the bank, it should print a message.
public void printAccountInfo(int accountNum, int n) {
    for (int i =0; i<numOfAccounts; i++) {
                        if (accountNum == accounts[i].getAccountNum()  ) {
                            System.out.println(accounts[i].getAccountInfo());
                            System.out.println(accounts[i].getTransactionInfo(n));
                            return;
                        }
                    }
    System.out.println("Account number not found.");
    }

}





  static class BankAccount{

       private int accountNum;
       private String customerName;
       private double balance;
       private double[] transactions;
       private int numOfTransactions;
       private  static int noOfAccounts=0;

       public String getAccountInfo(){
           return "Account number: " + accountNum + "\nCustomer Name: " + customerName + "\nBalance:" + balance +"\n";
       }

       public String getTransactionInfo(int n)
       {
            numOfTransactions = n;
            return n;

        }

       public BankAccount(String abc, double xyz){
         customerName = abc;
         balance = xyz;
         noOfAccounts ++;
         accountNum = noOfAccounts;
         transactions = new double[100];
         transactions[0] = balance;
         numOfTransactions = 1;
       }

    public int getAccountNum(){
        return accountNum;
    }
    public void deposit(double amount){

        if (amount<=0) {
            System.out.println("Amount to be deposited should be positive");
        } else {
            balance = balance + amount;
            transactions[numOfTransactions] = amount;
            numOfTransactions++;
        }
    }
    public void withdraw(double amount)
    {
        if (amount<=0){
             System.out.println("Amount to be withdrawn should be positive");
         }
        else
        {
            if (balance < amount) {
                System.out.println("Insufficient balance");
            } else {
                balance = balance - amount;
                transactions[numOfTransactions] = amount;
                numOfTransactions++;
            }
        }
    }

}//end of class
}

import java.util.Scanner；
公共类BankApp{
公共静态void main（字符串[]args）{
扫描仪s=新的扫描仪（System.in）；
银行myBank=新银行（）；
int user_choice=2；
做{
//向用户显示菜单
//询问用户的选择并验证它（确保它介于1和6之间）
System.out.println（）；
System.out.println（“1）开立新的银行账户”）；
系统输出打印（“2）存入银行账户”）；
系统输出打印（“3）提取到银行账户”；
System.out.println（“4）打印短期账户信息”）；
System.out.println（“5）打印详细的账户信息，包括最近的交易”）；
系统输出打印（“6）退出”）；
System.out.println（）；
系统输出打印（“输入选项[1-6]：”；
user_choice=s.nextInt（）；
开关（用户选择）{
案例1:System.out.println（“输入客户名称”）；
字符串cn=s.next（）；
系统输出打印项次（“输入期初余额”）；
双d=s.nextDouble（）；
System.out.println（“账户已创建，其编号如下：“+myBank.openNewAccount（cn，d））；
打破
案例2:System.out.println（“输入帐号”）；
int an=s.nextInt（）；
System.out.println（“输入存款金额”）；
双da=s.nextDouble（）；
我的银行存款给（安，da）；
打破
案例3:System.out.println（“输入帐号”）；
int acn=s.nextInt（）；
System.out.println（“输入提取金额”）；
双wa=s.nextDouble（）；
myBank.提款（华盛顿州acn）；
打破
案例4:System.out.println（“输入帐号”）；
int anum=s.nextInt（）；
myBank.printAccountInfo（anum）；
打破
//案例5：……断裂；
}
}
while（用户选择！=“6”）；
}
静态类库{
私人银行账户[]账户；//此银行的所有银行账户
private int numOfAccounts；//此银行的银行帐户数
//构造函数：新的银行对象最初不包含任何帐户。
公共银行（）{
账户=新银行账户[100]；
numOfAccounts=0；
}
//使用给定的客户名称和期初余额作为参数创建新的银行帐户
//和返回此新帐户的帐户号。它还将此帐户添加到帐户列表中
//银行调用对象的名称。
public int openNewAccount（字符串customerName，双重openingBalance）{
银行账户b=新银行账户（客户名称、期初余额）；
账户[numOfAccounts]=b；
NUMOF++；
返回b.getAccountNum（）；
}
//从给定帐号的帐户中提取给定金额。如果该帐户为
//在银行不可用，它应该打印一条消息。
公共作废取款（int accountNum，双倍金额）{
对于（int i=0；i将整数转换为字符串：

String out = Integer.toString(n);

如果希望以字符串形式返回事务数，而不是整数（存储为整数），则需要将整数转换为字符串

在Java中，您可以通过以下方式执行此操作：

Integer.toString(numOfTransactions)

旁注：出于好奇，在你的程序中，你为什么要这样做

public String gettransactionInfo(int n)
{
    numOfTransactions = n;
    return n;
}

这是低效和错误的，因为您正在将numberOfTransactions设置为n值。按照惯例，该功能放在setter方法中，而不是getter方法中，这是您的实现应该做的

理想情况下，它应该是：

public String gettransactionInfo()
{
    return Integer.toString(numOfTransactions);
}

编辑：

根据注释，正确的做法是从事务数组返回一个索引，对应于索引n

其中，在本例中，事务数组应为字符串数组

编辑2：

在使用单独的字符串数组的情况下，将按如下方式更新它（取决于事务）：

import java.util.Scanner;
public class BankApp {
public static void main(String[] args) {
    Scanner s = new Scanner(System.in);
    Bank myBank = new Bank();

    int user_choice = 2;

    do {
        //display menu to user
        //ask user for his choice and validate it (make sure it is between 1 and 6)
        System.out.println();
        System.out.println("1) Open a new bank account");
        System.out.println("2) Deposit to a bank account");
        System.out.println("3) Withdraw to bank account");
        System.out.println("4) Print short account information");
        System.out.println("5) Print the detailed account information including last transactions");
        System.out.println("6) Quit");
        System.out.println();
        System.out.print("Enter choice [1-6]: ");
        user_choice = s.nextInt();
        switch (user_choice) {
            case 1: System.out.println("Enter a customer name");
                    String cn = s.next();
                    System.out.println("Enter a opening balance");
                    double d = s.nextDouble();
                    System.out.println("Account was created and it has the following number: " + myBank.openNewAccount(cn, d));
                    break;
            case 2: System.out.println("Enter a account number");
                    int an = s.nextInt();
                    System.out.println("Enter a deposit amount");
                    double da = s.nextDouble();
                    myBank.depositTo(an, da);
                    break;
            case 3: System.out.println("Enter a account number");
                    int acn = s.nextInt();
                    System.out.println("Enter a withdraw amount");
                    double wa = s.nextDouble();
                    myBank.withdrawFrom(acn, wa);
                    break;
            case 4: System.out.println("Enter a account number");
                    int anum = s.nextInt();
                    myBank.printAccountInfo(anum);
                    break;
           case 5:  System.out.println("Enter a account number");
                    anum = s.nextInt();
                    myBank.printTransactionInfo(anum);
                    break;
          default: System.out.println("Invalid option. Please try again.");

        }
}
while (user_choice != '6');
}

static class Bank {
private BankAccount[] accounts;     // all the bank accounts at this bank
private int numOfAccounts;      // the number of bank accounts at this bank

    //Constructor: A new Bank object initially doesn’t contain any accounts.
public Bank() {
    accounts = new BankAccount[100];
    numOfAccounts = 0;
    }

// Creates a new bank account using the customer name and the opening balance given as parameters
// and returns the account number of this new account. It also adds this account into the account list
// of the Bank calling object.
public int openNewAccount(String customerName, double openingBalance) {

    BankAccount b = new BankAccount(customerName, openingBalance);
    accounts[numOfAccounts] = b;
    numOfAccounts++;
    return b.getAccountNum();
}

// Withdraws the given amount from the account whose account number is given. If the account is
// not available at the bank, it should print a message.
public void withdrawFrom(int accountNum, double amount) {
    for (int i =0; i<numOfAccounts; i++) {
        if (accountNum == accounts[i].getAccountNum()  ) {
            accounts[i].withdraw(amount);
            System.out.println("Amount withdrawn successfully");
            return;
        }
    }
    System.out.println("Account number not found.");
    }

// Deposits the given amount to the account whose account number is given. If the account is not
// available at the bank, it should print a message.
public void depositTo(int accountNum, double amount) {
    for (int i =0; i<numOfAccounts; i++) {
        if (accountNum == accounts[i].getAccountNum()  ) {
            accounts[i].deposit(amount);
            System.out.println("Amount deposited successfully");
            return;
        }
    }
    System.out.println("Account number not found.");
}

// Prints the account number, the customer name and the balance of the bank account whose
// account number is given. If the account is not available at the bank, it should print a message.
public void printAccountInfo(int accountNum) {
    for (int i =0; i<numOfAccounts; i++) {
                if (accountNum == accounts[i].getAccountNum()  ) {
                    System.out.println(accounts[i].getAccountInfo());
                    return;
                }
            }
    System.out.println("Account number not found.");
}

public void printTransactionInfo(int accountNum) {
    for (int i =0; i<numOfAccounts; i++) {
                if (accountNum == accounts[i].getAccountNum()  ) {
                    System.out.println(accounts[i].getAccountInfo());
                    System.out.println("Last transaction: " + accounts[i].getTransactionInfo(accounts[i].getNumberOfTransactions()-1));
                    return;
                }
            }
    System.out.println("Account number not found.");
}


// Prints the account number, the customer number and the balance of the bank account whose
// account number is given, together with last n transactions on that account. If the account is not
// available at the bank, it should print a message.
public void printAccountInfo(int accountNum, int n) {
    for (int i =0; i<numOfAccounts; i++) {
                        if (accountNum == accounts[i].getAccountNum()  ) {
                            System.out.println(accounts[i].getAccountInfo());
                            System.out.println(accounts[i].getTransactionInfo(n));
                            return;
                        }
                    }
    System.out.println("Account number not found.");
    }

}
    static class BankAccount{

       private int accountNum;
       private String customerName;
       private double balance;
       private double[] transactions;
       private String[] transactionsSummary;
       private int numOfTransactions;
       private  static int noOfAccounts=0;

       public String getAccountInfo(){
           return "Account number: " + accountNum + "\nCustomer Name: " + customerName + "\nBalance:" + balance +"\n";
       }

       public String getTransactionInfo(int n)
       {
            String transaction = transactionsSummary[n];
            if (transaction == null) {
                return "No transaction exists with that number.";
            }
            else {
                return transaction;
            }
        }

       public BankAccount(String abc, double xyz){
         customerName = abc;
         balance = xyz;
         noOfAccounts ++;
         accountNum = noOfAccounts;
         transactions = new double[100];
         transactionsSummary = new String[100];
         transactions[0] = balance;
         transactionsSummary[0] = "A balance of : $" + Double.toString(balance) + " was deposited.";
         numOfTransactions = 1;
       }

    public int getAccountNum(){
        return accountNum;
    }

    public int getNumberOfTransactions() {
        return numOfTransactions;
    }

    public void deposit(double amount){

        if (amount<=0) {
            System.out.println("Amount to be deposited should be positive");
        } else {
            balance = balance + amount;
            transactions[numOfTransactions] = amount;
            transactionsSummary[numOfTransactions] = "$" + Double.toString(amount) + " was deposited.";
            numOfTransactions++;
        }
    }
    public void withdraw(double amount)
    {
        if (amount<=0){
             System.out.println("Amount to be withdrawn should be positive");
         }
        else
        {
            if (balance < amount) {
                System.out.println("Insufficient balance");
            } else {
                balance = balance - amount;
                transactions[numOfTransactions] = amount;
                transactionsSummary[numOfTransactions] = "$" + Double.toString(amount) + " was withdrawn.";
                numOfTransactions++;
            }
        }
    }

    }//end of class
}

import java.util.Scanner；
公共类BankApp{
公共静态void main（字符串[]args）{
扫描仪s=新的扫描仪（System.in）；
银行myBank=新银行（）；
int user_choice=2；
做{
//向用户显示菜单
//询问用户的选择并验证它（确保它介于1和6之间）
System.out.println（）；
System.out.println（“1）开立新的银行账户”）；
系统输出打印（“2）存入银行账户”）；
系统输出打印（“3）提取到银行账户”；
System.out.println（“4）打印短期账户信息”）；
System.out.println（“5）打印详细的账户信息，包括最近的交易”）；
系统输出打印（“6）退出”）；
System.out.println（）；
系统输出打印（“输入选项[1-6]：”；
user_choice=s.nextInt（）；
开关（用户选择）{
案例1:System.out.println（“输入客户名称”）；
字符串cn=s.next（）；
系统输出打印项次（“输入期初余额”）；
双d=s.nextDouble（）；
System.out.println（“账户已创建，其编号如下：“+myBank.openNewAccount（cn，d））；
打破
案例2:System.out.println（“输入账户
public String gettransactionInfo(int n)
{
    numOfTransactions = n;
    return n;
}

transInfo[0] = "A deposited 30K"
transInfo[1] = "B withdrew 20K"
transInfo[2] = "C deposited 5k"

    public String gettransactionInfo(int n)
{
  //Traverse the "transactions" array in *reverse* order
  //In For loop start with transactions.length, and decrement by 1 "n" times
  // Append the transaction amount to a String
 // Return the string.
}