我几乎完成了一项任务。我正在创建一个银行程序，我几乎已经完成了所有工作。我坚持的部分是交易部分。我必须创建一个函数public String getTransactionInfo(int n)来返回银行账户的最后 n 笔交易。我似乎无法弄清楚这部分。我有一个变量private int numOfTransactions，我尝试将其合并到函数中，但它没有用。这就是我尝试过的。
public String gettransactionInfo(int n)
{
numOfTransactions = n;
return n;
}
那没有用。无法弄清楚如何返回这是一个字符串。有任何想法吗？
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
}