Question

所以，作为免责声明，我对编程非常陌生，可能会遗漏一些明显的东西。现在，我试图创建两个名为withdraw（）和deposit（）的方法，这将允许我更改字段currentBalance的值，但是，每次我尝试用我的两个方法更改currentBalance的值时，我检查使用我的方法getBalance（）的字段值，它始终保持不变。

class TradingService{

   public class Trader {

      //This field stores the trader's name
      private String traderName;

      //This field stores the trader's current balance
      private double currentBalance;

      //A constructor to create a Trader
      public Trader(String traderName) {
        this.traderName = traderName;
      }

      //This method gets returns the trader's name
      public String getName() {
        return traderName;
      }

      //This method set's the trader's name
      public void setName(String traderName) {
        this.traderName = traderName;
      }

      //This method decreases the trader's balance
      public void withdraw(double withdrawAmount) {
        this.currentBalance = (currentBalance - withdrawAmount);
      }

      //This method increases the trader's balance
      public void deposit(double depositAmount) {
        this.currentBalance = (currentBalance + depositAmount);
      }

      //This method returns the trader's current balance
      public double getBalance() {
        return currentBalance;
      }

   }

}

我正在使用DrJava，我正在交互面板中测试我的代码。这是我测试的结果。

> Trader t1
> t1 = new Trader("Bill")
Trader@22e1cbe4
> t1.deposit(10.0)
10.0
> t1.getBalance()
0.0

我已经完成了我可以想象的所有修复代码的事情，但我没有想法，我不认为在我的代码中再输入3个小时的随机内容会做很多事情。

感谢您抽出宝贵时间阅读我的问题。

Answer 1

下面的代码工作正常。我不确定Java博士是什么，但代码按预期工作。

public class TradingService {

    class Trader {

        //This field stores the trader's name
        private String traderName;

        //This field stores the trader's current balance
        private double currentBalance;

        //A constructor to create a Trader
        public Trader(String traderName) {
            this.traderName = traderName;
        }

        //This method gets returns the trader's name
        public String getName() {
            return traderName;
        }

        //This method set's the trader's name
        public void setName(String traderName) {
            this.traderName = traderName;
        }

        //This method decreases the trader's balance
        public void withdraw(double withdrawAmount) {
            this.currentBalance = (currentBalance - withdrawAmount);
        }

        //This method increases the trader's balance
        public void deposit(double depositAmount) {
            this.currentBalance = (currentBalance + depositAmount);
        }

        //This method returns the trader's current balance
        public double getBalance() {
            return currentBalance;
        }
    }

    public static void main(String[] args) {
        TradingService service = new TradingService();
        TradingService.Trader trader = service.new Trader("trader");
        System.out.println("Balance before deposit:\n" + trader.getBalance());
        trader.deposit(10.00);
        System.out.println("Balance after deposit:\n" + trader.getBalance());
    }
}

输出：

Balance before deposit:
0.0
Balance after deposit:
10.0

Answer 2

班级“Trader”看起来很好并为我工作。但是你有一个“Trader”什么是“TradingService”类中的公共类，我认为这个类可能没有编译而且你正在执行一个旧文件，你可以像“内部类”一样尝试使用“Trader”类。

class Trader {

  //This field stores the trader's name
  private String traderName;

  //This field stores the trader's current balance
  private double currentBalance;

  //A constructor to create a Trader
  public Trader(String traderName) {
    this.traderName = traderName;
  }

  //This method gets returns the trader's name
  public String getName() {
    return traderName;
  }

  //This method set's the trader's name
  public void setName(String traderName) {
    this.traderName = traderName;
  }

  //This method decreases the trader's balance
  public void withdraw(double withdrawAmount) {
    this.currentBalance = (currentBalance - withdrawAmount);
  }

  //This method increases the trader's balance
  public void deposit(double depositAmount) {
    this.currentBalance = (currentBalance + depositAmount);
  }

  //This method returns the trader's current balance
  public double getBalance() {
    return currentBalance;
  }
}

public class TradingService{

    public static void main(String[] args)
    {

      Trader t = new Trader("test");
      t.deposit(10);
      System.out.print(t.getBalance());

    }
}

在Java中更改字段值时遇到麻烦

2 个答案: