Java 银行账户计划问题

对于我的Java类，我们需要创建一个银行帐户，该帐户具有取款、存款和显示当前余额的方法。在Tester类中，我想让它询问名称、余额，然后允许您选择1、2或3。然后它重复您选择的选项，直到您说键入“n”。问题是，运行此代码会导致在您存款后显示“您在帐户（帐户名称）中存款（存款金额）。您的新余额是（this）。”其中显示“this”的部分与存款金额完全相同。换言之，它并没有加上它，它只是使新的余额与存款相同，不管以前存了多少。有什么帮助吗？谢谢

import java.io.*;
import java.util.*;
public class BankAccount
{
    public BankAccount(double b, String n)
    {
        double balance = b;
        String name = n;
    }
    public void deposit(double d)
    {
        balance += d;
    }
    public void withdraw(double w)
    {
        balance -= w;
    }
    public String nickname()
    {
        System.out.print("Enter a new name: ");
        Scanner kbIn = new Scanner(System.in);
        String n = kbIn.nextLine();
        return n;
    }
    double balance;
    String name;
}

和测试仪类别：

import java.io.*;
import java.util.*;
public class Tester
{
    public static void main(String args[])
    {
        Scanner kbInLine = new Scanner(System.in);
        Scanner kbIn = new Scanner(System.in);

        System.out.print("Enter your name: ");
        String name = kbInLine.nextLine();

        System.out.print("Please enter balance: $");
        double balance = kbIn.nextDouble();

        BankAccount myAccount = new BankAccount(balance, name);
        String proceed = "y";

        while(proceed.equalsIgnoreCase("y"))
        {
            System.out.println("\nPlease pick a number. Would you like to...\n\t 1. Deposit\n\t 2. Withdraw\n\t 3. Print Balance\n");
            int choice = kbIn.nextInt();

            switch(choice)
            {
                case 1:
                    System.out.print("How much would you like to deposit?\n\t$");
                    double deposit = kbIn.nextDouble();
                    myAccount.deposit(deposit);
                    System.out.println("You have deposited $" + deposit + " into the account of " + name + ". The new balance is: " + myAccount.balance);
                    break;
                case 2:
                    System.out.print("How much would you like to withdraw?\n\t$");
                    double withdraw = kbIn.nextDouble();
                    if(myAccount.balance - withdraw > 0)
                    {
                        myAccount.withdraw(withdraw);
                        System.out.println("You have withdrawn $" + withdraw + " from the account of " + name + ". The new balance is: " + myAccount.balance);
                    }
                    else    
                    {
                        System.out.println("Sorry, you have insufficient funds for this operation. Your existing balance is $" + myAccount.balance);
                    }
                    break;
                case 3:
                    System.out.print("The balance in the account of " + name + " is $" + myAccount.balance);
                    break;
            }
            System.out.print("\nWould you like to do another transaction? (Y/N)");
            proceed = kbIn.next();
        }
        System.out.println("\nThank you for banking with us. Have a good day!");
    }
}

真正有趣的是，在这之前我做了一个项目（实际上是一个简化版本），它先存款，然后提取预先确定的编码金额，然后输出新的银行余额，这样做很好。但银行余额的代码是相同的。这是代码。
银行账户类别为：

public class BankAccount
{
    public BankAccount(String nm, double amt) // Constructor
    {
        name = nm;
        balance = amt;
    }
    public void deposit(double d) // Sets up deposit object as balance += d
    {
        balance += d;
    }
    public void withdraw(double w) // Sets up withdraw object as balance -= w
    {
        balance -= w;
    }

    public double balance;
    public String name;
}

import java.io.*;
import java.util.*;
public class Tester
{
    public static void main(String args[])
    {
        Scanner kbIn = new Scanner(System.in);
        System.out.print("Enter your name:");
        String name = kbIn.nextLine();

        System.out.print("Enter the balance:");
        double balance = kbIn.nextDouble();

        BankAccount myAccount = new BankAccount(name, balance);
        myAccount.deposit(505.22);
        System.out.println(myAccount.balance);
        myAccount.withdraw(100.00);

        System.out.println("The " + myAccount.name + " account balance is, $" + myAccount.balance);
    }
}

测试仪类别为：

public class BankAccount
{
    public BankAccount(String nm, double amt) // Constructor
    {
        name = nm;
        balance = amt;
    }
    public void deposit(double d) // Sets up deposit object as balance += d
    {
        balance += d;
    }
    public void withdraw(double w) // Sets up withdraw object as balance -= w
    {
        balance -= w;
    }

    public double balance;
    public String name;
}

import java.io.*;
import java.util.*;
public class Tester
{
    public static void main(String args[])
    {
        Scanner kbIn = new Scanner(System.in);
        System.out.print("Enter your name:");
        String name = kbIn.nextLine();

        System.out.print("Enter the balance:");
        double balance = kbIn.nextDouble();

        BankAccount myAccount = new BankAccount(name, balance);
        myAccount.deposit(505.22);
        System.out.println(myAccount.balance);
        myAccount.withdraw(100.00);

        System.out.println("The " + myAccount.name + " account balance is, $" + myAccount.balance);
    }
}

---

您实际上并没有在此处初始化您的

余额
成员变量：

public BankAccount(double b, String n)
{
    double balance = b;

这将创建一个名为
balance
的新局部变量，您将
b
的值分配给该变量。运行此构造函数后，成员变量余额将保持为0（默认值）

公共银行账户（双b，字符串n）
{
双平衡=b；
字符串名=n；
}

--->

公共银行账户（双b，字符串n）
{
这个平衡=b；
this.name=n；
}
或者您可以将balance声明为static（数据类字段），并将使用此变量的方法也声明为static。
是的，他正在创建一个局部变量来隐藏类字段。我真的不知道为什么，但是我做了另一个项目（这是它的扩展）通过存款和提取预定金额，并仅说明银行余额，简化了这一过程。它可以这样做，但它是完全相同的bankaccount类。我会在上面的更新中发布这些信息。好的，我想我知道了。在第一个例子中（它不起作用），我通过说“double”或“string”来重新初始化我的状态变量。在第二个应用程序中，我只是通过不包含“String”将它们声明为一个值。谢谢你的帮助！对，在第一个例子中，您创建了与成员变量同名的新局部变量。分配给这些局部变量不会更改成员变量。在第二个示例中，您将分配给成员变量，这是您想要的。我不知道“this”是什么意思，我现在正在查找它。但这起了作用。谢谢。还有，你知道以前的项目中的代码为什么有效吗？（我更新了我的帖子，所以它显示了旧的项目）。我的英语很差，所以我不能用英语向你解释。对不起。