Java ATM程序

Question

我正在做一个自动取款机程序，我很难弄清楚如何让它真正存取款。余额自动开始为$0，但是我不能得到我输入的任何东西来实际增加或减去它，我做错了什么？

public class ATM {
static Scanner keyboard = new Scanner(System.in);
static String acctNum, pwd, result;
static double oldBalance, newBalance, deposit, withdraw;
static int choose;

public static void main(String[] args) {
    for (int run = 0; run < 3; run++) {
        System.out.println("Enter your account number");
        acctNum = keyboard.nextLine();
        System.out.println("Enter your account password");
        pwd = keyboard.nextLine();

        result = checkID(acctNum, pwd);
        if (!result.equals("ERROR")) {
            break;
        } else if (run == 2) {// you cannot try to log in anymore than 3
                                // times
            System.out.println("MAXIMUM TRIES EXCEEDED");
            return;
        }

    }
    menu();
}

public static String checkID(String acctNum, Object pwd) {
    String result = "ERROR";
    String a = "44567-5 mypassword 520.36";
    String b = "1234567-6 anotherpassword 48.20";
    String c = "4321-0 betterpassword 96.74";

    if (acctNum.equals("44567-5") && pwd.equals("mypassword")) {
        result = "520.36";
    } else if (acctNum.equals("1234567-6") && pwd.equals("anotherpassword")) {
        result = "48.20";
    } else if (acctNum.equals("4321-0") && pwd.equals("betterpassword")) {
        result = "96.74";
    }
    System.out.println(result);
    return result;
}

public static int menu() {
    System.out
            .println("Choose one of the following: \n1.Display Balance\n2.Deposit\n3.Withdraw\n4.Log Out");
    choose = keyboard.nextInt();

    if (choose == 1) {// 1. Display Balance
        displayBalance();
        menu();
        return 1;

    }
    if (choose == 2) {// 2. Deposit
        deposit();
        menu();
        return 2;

    }
    if (choose == 3) {// 3. Withdraw
        withdraw();
        menu();
        return 3;

    }
    if (choose == 4) {// 4. Log out
        System.out.println("You are logged out.");
        return 4;

    }
    if (choose <= 5) {// type in anything greater than 4 and you will get a
                        // system error
        System.out.println("System Error");
        menu();
        return 5;
    }
    if (choose >= 1) {// type in anything less than 1 and you will get a
                        // system error
        System.out.println("System Error");
        menu();
        return 6;
    }
    return choose;

}

public static double deposit() {
    System.out.println("How much would you like to deposit?");
    deposit = keyboard.nextInt();
    System.out.println((deposit + oldBalance)==newBalance);// deposit money into balance
    return 2;
}

public static double displayBalance() {
    System.out.println("Total balance is: $" + oldBalance);
    oldBalance = 0.00;
    return 1;
}

public static double withdraw() {
    System.out.println("How much would you like to withdraw?");
    withdraw = keyboard.nextInt();
    System.out.println(newBalance + withdraw);// withdraw money from balance
    return 3;
}

}

Answer 1

以下是一些观察结果：

1. 您的类不应该将oldBalance、global和deposit声明为全局变量。取款方法不应该访问存款变量，反之亦然。尽可能地限制变量的作用域是一种很好的编程实践。因为在此方法之外并不真正需要“存款”变量，所以绝对没有理由将其设置为全局变量。但“当前余额”就不能这么说了。这个变量是这个类的所有方法都需要的:存款、提款、displayBalance等。因此，有一个很好的理由让它成为全局的(但是，如果你可以用较小的范围解决问题，你应该这样做)。
2. 我不明白为什么deposit()和withdrawal()需要返回任何东西。

deposit()和withdrawal()最简单的实现是简单地将用户输入添加到currentBalance并将其保存在currentBalance中。

public void deposit()
{
   Scanner input = new Scanner(System.in);
   System.out.printn("Enter deposit amount: );
   double amount = input.nextDouble();
   System.out.println("Your deposit amount: " + amount);
   currentBalance += amount;
   System.out.println("Your new balance is: + currentBalance);
}

public void withdrawal()
{
   Scanner input = new Scanner(System.in);
   System.out.printn("Enter withdrawal amount: );
   double amount = input.nextDouble();
   System.out.println("Your withdrawal amount: " + amount);
   currentBalance -= amount;
   System.out.println("Your new balance is: + currentBalance);
}

您永远不会保存当前余额。==运算符是比较运算符，而不是赋值运算符。当你这样做的时候：

System.out.println((deposit + oldBalance)==newBalance);

或者像这样：

System.out.println(newBalance + withdraw);

您所要做的就是将值传递给println()方法，而不是更新应该保持余额的变量。实际上，第一个应该打印存款(除非false和oldBalance都为零)。在我的代码示例中，currentBalance += amount;是currentBalance = currentBalance + amount;的缩写，意思是“将这个amount添加到currentBalance中并将其存储在currentBalance中。因为我重用了currentBalance，所以不再需要oldBalance变量。

Answer 2

完全运行的代码

import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowEvent;
import java.awt.event.WindowAdapter;
import java.io.IOException;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import java.util.ArrayList;
import java.util.Scanner;

/**
   A simulation of an automatic teller machine
*/

public class ATM  {
static Scanner keyboard = new Scanner(System.in);
static String acctNum, pwd, result;
static double oldBalance, newBalance, deposit, withdraw,currentBalance;
static int choose;

public static void main(String[] args) {
    for (int run = 0; run < 3; run++) {
        System.out.println("Enter your account number");
        acctNum = keyboard.nextLine();
        System.out.println("Enter your account password");
        pwd = keyboard.nextLine();

        result = checkID(acctNum, pwd);
        if (!result.equals("ERROR")) {
            break;
        } else if (run == 2) {// you cannot try to log in anymore than 3
                                // times
            System.out.println("MAXIMUM TRIES EXCEEDED");
            return;
        }

    }
    menu();
}

public static String checkID(String acctNum, Object pwd) {
    String result = "ERROR";
    String a = "44567-5 mypassword 520.36";
    String b = "1234567-6 anotherpassword 48.20";
    String c = "4321-0 betterpassword 96.74";

    if (acctNum.equals("2345") && pwd.equals("2345")) {
        result = "520.36";
    } else if (acctNum.equals("1234567-6") && pwd.equals("anotherpassword")) {
        result = "48.20";
    } else if (acctNum.equals("4321-0") && pwd.equals("betterpassword")) {
        result = "96.74";
    }
    System.out.println(result);
    return result;
}

public static int menu() {
    System.out.println("Choose one of the following: \n1.Display Balance\n2.Deposit\n3.Withdraw\n4.Log Out");
    choose = keyboard.nextInt();

    if (choose == 1) {// 1. Display Balance
        displayBalance();
        menu();
        return 1;

    }
    if (choose == 2) {// 2. Deposit
        deposit();
        menu();
        return 2;

    }
    if (choose == 3) {// 3. Withdraw
        withdraw();
        menu();
        return 3;

    }
    if (choose == 4) {// 4. Log out
        System.out.println("You are logged out.");
        return 4;

    }
    if (choose <= 5) {// type in anything greater than 4 and you will get a
                        // system error
        System.out.println("System Error");
        menu();
        return 5;
    }
    if (choose >= 1) {// type in anything less than 1 and you will get a
                        // system error
        System.out.println("System Error");
        menu();
        return 6;
    }
    return choose;

}

public static void deposit()
{
   Scanner input = new Scanner(System.in);
   System.out.println("Enter deposit amount:");
   double amount = input.nextDouble();
   System.out.println("Your deposit amount: " + amount);
   currentBalance += amount;
   System.out.println("Your new balance is: " + currentBalance);
}

public static double displayBalance() {
    System.out.println("Total balance is: $" + currentBalance);
    oldBalance = 0.00;
    return 1;
}

public static void withdraw()
{
   Scanner input = new Scanner(System.in);
   System.out.println("Enter withdrawal amount: ");
   double amount = input.nextDouble();
   System.out.println("Your withdrawal amount: " + amount);
   currentBalance -= amount;
   System.out.println("Your new balance is: " + currentBalance);
}
}

Answer 3

    package shraam.bank.atm;

    import java.util.HashMap;
    import java.util.Map;
    import java.util.Scanner;
    import java.util.logging.Level;


    public class CalculateMoneyAtm {
        static Integer initialtwothousandrupees = 0;
        static Integer initialhundressrupees = 0;
        static Integer initialfiftyrupees = 0;
        static Integer initialtenrupees = 0;

        static Integer twothousandrupees = 0;
        static Integer hundressrupees = 0;
        static Integer fiftyrupees = 0;
        static Integer tenrupees = 0;
        static Integer totalAmount = 0;

        public static void main(String[] args) {

            ATMStatus atmStatus = new ATMStatus();
            getMoney(atmStatus);

        }//end of psvm

        public static void reRun(ATMStatus atmStatus) {
            MyLog.logit().info("Would u like to credit more money ? y/n");
            System.out.println("Would u like to credit more money ? y/n ");
            Scanner input = new Scanner(System.in);
            String choice = input.nextLine();
            if (choice.equals("y") || choice.equals("Y")) {
                getMoney(atmStatus);
            }
            if (choice.equals("n") || choice.equals("N")) {
                System.exit(1);
            } else {
                MyLog.logit().log(Level.SEVERE, "Invalid Input :"+choice);
                System.out.println("Invalid Input");
            }
            reRun(atmStatus);
        }

        public static void getMoney(ATMStatus atmStatus) {
            twothousandrupees = 0;
             hundressrupees = 0;
             fiftyrupees = 0;
             tenrupees = 0;
             totalAmount = 0;
            Integer amountInt=0;
            System.out.println("Currency Avaialbe in ATM");
            for (String key : atmStatus.getAvaialableMoney().keySet()) {
                System.out.println(atmStatus.getAvaialableMoney().get(key) + ":"
                        + key + " Notes");
            }

            for (String key : atmStatus.getAvaialableMoney().keySet()) {
                if (key.equals("2000"))
                    initialtwothousandrupees = atmStatus.getAvaialableMoney().get(key);
                if (key.equals("100"))
                    initialhundressrupees = atmStatus.getAvaialableMoney().get(key);
                if (key.equals("50"))
                    initialfiftyrupees = atmStatus.getAvaialableMoney().get(key);
                if (key.equals("10"))
                    initialtenrupees = atmStatus.getAvaialableMoney().get(key);
            }

            Scanner input = new Scanner(System.in);
            System.out.print("Enter Money > ");
            String amount = input.nextLine();
            try {
                try{
                 amountInt = Integer.parseInt(amount);
                 if(amountInt%10!=0)
                 {
                     System.out.println("Please enter amount in multiple of 10 ");
                     reRun(atmStatus);
                 }
                }catch(NumberFormatException ne){
                    MyLog.logit().log(Level.SEVERE, ne.getMessage());
                }
                System.out.print("Required Amount : ");
                System.out.println(amount);

                totalAmount = ((initialtwothousandrupees * 2000) + (initialhundressrupees * 100)
                        + (initialfiftyrupees * 50) + (initialtenrupees * 10));
                System.out
                        .println("Total Available amount in ATM : " + totalAmount);
                if (totalAmount < amountInt) {
                    System.out
                            .println("Total Avaialble amount is less in atm, Sorry for Inconvience");
                     reRun(atmStatus);
                }


                while (amountInt >= 2000 && initialtwothousandrupees > 0) {
                    initialtwothousandrupees = initialtwothousandrupees - 1;
                    twothousandrupees++;
                    amountInt = amountInt - 2000;
                }

                while (amountInt >= 100 && initialhundressrupees > 0) {
                    initialhundressrupees = initialhundressrupees - 1;
                    hundressrupees++;
                    amountInt = amountInt - 100;
                }

                while (amountInt >= 50 && initialfiftyrupees > 0) {
                    initialfiftyrupees = initialfiftyrupees - 1;
                    fiftyrupees++;
                    amountInt = amountInt - 50;
                }
                while (amountInt >= 10 && initialtenrupees > 0) {
                    initialtenrupees = initialtenrupees - 1;
                    tenrupees++;
                    amountInt = amountInt - 10;
                }
                if (amountInt > 0) {
                    System.out.println("No avalable balance in this unit");
                    reRun(atmStatus);
                } else {
                    System.out.println("Plz take your money in currency");
                    Map<String, Integer> avaialableMoney = new HashMap<String, Integer>();
                    System.out.println("     No of 2000:"+ twothousandrupees);
                    System.out.println("     No of 100:"+ hundressrupees);
                    System.out.println("     No of 50:"+ fiftyrupees);
                    System.out.println("     No of 10:"+ tenrupees);
                    avaialableMoney.put("2000", (initialtwothousandrupees));
                    avaialableMoney.put("100", (initialhundressrupees));
                    avaialableMoney.put("50", (initialfiftyrupees));
                    avaialableMoney.put("10", (initialtenrupees));
                    atmStatus.setAvaialableMoney(avaialableMoney);
                }
                //return amountInt;
            } catch (Exception e) {
                MyLog.logit().log(Level.SEVERE, e.getMessage());
            }
            System.out.println("Take your Amount = "+(2000*twothousandrupees+100*hundressrupees+50*fiftyrupees+10*tenrupees));
            reRun(atmStatus);

        }//end of getMoney
    }

    package shraam.bank.atm;

    import java.util.HashMap;
    import java.util.Map;
    import java.util.logging.Level;

    public class ATMStatus {
        public  Map<String,Integer> avaialableMoney=new HashMap<String,Integer>();
        public ATMStatus(){
                MyLog.logit().log(Level.INFO, " ATMStatus Initialized");

        avaialableMoney.put("2000", 10);
        avaialableMoney.put("100", 10);
        avaialableMoney.put("50", 10);
        avaialableMoney.put("10", 10);
        }
        public  Map<String, Integer> getAvaialableMoney() {
            return this.avaialableMoney;
        }
        public void setAvaialableMoney(Map<String, Integer> avaialableMoney) {
            this.avaialableMoney = avaialableMoney;
        }

    }

    package shraam.bank.atm;

    import java.io.IOException;
    import java.util.logging.FileHandler;
    import java.util.logging.Logger;
    import java.util.logging.SimpleFormatter;

    public class MyLog {

        public static Logger logit()
        {
            Logger logger = Logger.getLogger("MyLog");  
            FileHandler fh;  

            try {  

                // This block configure the logger with handler and formatter  
                fh = new FileHandler("C:/ArunTest/temp/MyLogFile.log");  
                logger.addHandler(fh);
                SimpleFormatter formatter = new SimpleFormatter();  
                fh.setFormatter(formatter);  

                // the following statement is used to log any messages  
                logger.info("My first log");  

            } catch (SecurityException e) {  
                e.printStackTrace();  
            } catch (IOException e) {  
                e.printStackTrace();  
            }
            return logger;  
        }

    }
//
output:
Nov 27, 2016 10:43:48 PM shraam.bank.atm.MyLog logit
INFO: My first log
Nov 27, 2016 10:43:48 PM shraam.bank.atm.ATMStatus <init>
SEVERE:  ATMStatus 
Currency Avaialbe in ATM
10:100 Notes
10:2000 Notes
10:50 Notes
10:10 Notes
Enter Money > 540
Required Amount : 540
Total Available amount in ATM : 21600
Plz take your money in currency
     No of 2000:0
     No of 100:5
     No of 50:0
     No of 10:4
Take your Amount = 540
Nov 27, 2016 10:43:52 PM shraam.bank.atm.MyLog logit
INFO: My first log
Nov 27, 2016 10:43:52 PM shraam.bank.atm.CalculateMoneyAtm reRun
INFO: Would u like to credit more money ? y/n
Would u like to credit more money ? y/n 
y
Currency Avaialbe in ATM
5:100 Notes
10:2000 Notes
10:50 Notes
6:10 Notes
Enter Money > 2060
Required Amount : 2060
Total Available amount in ATM : 21060
Plz take your money in currency
     No of 2000:1
     No of 100:0
     No of 50:1
     No of 10:1
Take your Amount = 2060
Nov 27, 2016 10:44:04 PM shraam.bank.atm.MyLog logit
INFO: My first log
Nov 27, 2016 10:44:04 PM shraam.bank.atm.CalculateMoneyAtm reRun
INFO: Would u like to credit more money ? y/n
Would u like to credit more money ? y/n