Java编译器不会从同一文件夹中的另一个Java文件中找到方法？

Question

我们的任务是获取老师给我们的代码，并在单独的 java 文件中编写该代码调用的方法。之后，我们应该把它放在同一个文件夹中。这是他给我们的代码：

import java.util.Scanner;

public class CSCD210Lab9
{
   public static void main(String [] args)
   {
      Scanner kb = new Scanner(System.in);

      String name = null;
      double height, weight;

      do
      {
         name = Lab9Methods.readName(kb);
         height = Lab9Methods.readInfo(kb, "height");
         weight = Lab9Methods.readInfo("weight", kb);
         Lab9Methods.displayResults(name, height, weight, Lab9Methods.calcBMI(height, weight));

      }while(Lab9Methods.goAgain(kb)); 

   }// end main

}// end class

我已经编译了我在其中编写方法的文件，它编译得很好，完全没有错误。但是，当我马上去编译这段代码时，编译器指向每个编写 Lab9Methods 的实例，并给出错误“错误：找不到符号”。

我不明白为什么它不会从另一个文件中读取方法，即使两个文件都在同一个文件夹中。难道我做错了什么？

编辑

这是我的 Lab9Methods 类的代码。

import java.util.Scanner;

public class Lab9Methods
{



      public static String readName(final Scanner kb)throws Exception 
      {
      if(kb == null)
         throw new RuntimeException("Precondition not met");

         String name;
         System.out.println("Please enter the person's name: ");
         name = kb.nextLine();

         return name;    
      }


      public static double readInfo(final Scanner kb, final String str)
      {

      System.out.println("Please enter your" + str + ";");

      double height = kb.nextDouble();

      return height; 
      }


      public static double readInfo(final String str ,final Scanner kb)
      {


      System.out.println("Please enter your" + str + ";");
      double weight = readInfo(kb,str);

      return weight;

      }

      public static int calcBMI(double height, double weight)
      {
      int calcBMI = (int)(weight/((height * height) * 703));

      return calcBMI ;


      }


      public static void displayResults(final String name, final double height, final double weight, final double bmi)
      {

      System.out.println(name + "with a weight of" + weight + "and a height of" + height + " " + bmi);
      if(bmi < 18.5)
      { 
        System.out.println("You are underweight");
      }
      else if(bmi > 18.6 && bmi < 24.9)
      {  
        System.out.println("You are normal");
      }
      else if(bmi > 25.1 && bmi < 29.9)
      {
        System.out.println("You are overweight");
      }
      else if(bmi > 29.9)
      {
        System.out.println("You are obese");
      }        
    }

    public static boolean goAgain(final Scanner kb)
    {
        boolean goAgain = false;
        String answer;
        System.out.println("Do you want to go again (Yes/No) :");
        answer = kb.nextLine();

        while(!answer.equals("yes") && !answer.equals("no"))
        {
         System.out.print("Error re-try, Do you want to go again (Yes/No) :");
         answer = kb.nextLine();
        }
        if(answer.equals("yes"))
        { 
         goAgain = true; 
        }
        else if(answer.equals("no"))
        {
         goAgain = false;
        }
        return goAgain;
    }    

 }

Answer 1

尝试下载 IDE（例如 Eclipse 或 IntelliJ 社区版）并在其中执行项目。我的猜测是你需要声明应该映射到你的类所在目录的“包”。

告诉你的导师他的风格更像 C 而不是 Java，而且 //end main 和 //end class 很久以前就过时了；）