java - 错误找不到简单投资类别的符号

Question

您好，我不知道为什么我收到错误无法找到我的简单投资类的符号，这是一个编译器错误。

public class Investments
{
   //instance variables 
   private double moneyInvested;
   private double investRate;
   private int numOfYears;

   //construscts a investment with the parameters moneyInvested, double investRate, int numOfYears
    public Investments(double moneyInvested, double investRate, int numOfYears)
   {  
      double amount = moneyInvested;
      double rate = investRate;
      int time = numOfYears;
   }

   public double ruleOf72()
   {  
      return (72/rate);
   }

   public int simpleAnnual()
   {
      return  Math.round(amount * Math.pow(1 + rate, time));
   }

   public int compoundAnnual()
   {  
      return  Math.round(amount * Math.pow((1 +rate)^time));
   }

}

Answer 1

此处声明的变量

double amount = moneyInvested;
double rate = investRate;
int time = numOfYears;

都是local variables 。它们不能在它们定义的 block 之外访问，即。在构造函数主体之外。

您可能想使用实例字段。

this.moneyInvested = moneyInvested;
// ... etc.

您应该重构代码的其余部分以也使用这些实例变量。