Question

我收到错误：

Driver2.java:22: error: method readInitialFromFile in class VectorofContact cannot be applied to given types;
     v.readInitialFromFile("contacts");
                           ^
required: no arguments
found: String
reason: actual and formal argument lists differ in length

我得到此错误的方法应该从文件中读取。在发布我的代码之前，我将介绍一下我的代码。我正在写一本小而简单的地址簿。我有一个“Contact class”，它有一个no-arg构造函数和一些getter和setter。

我的Driver2课程的评论正在进行中，您可以忽略这些评论。

这是我的VectorofContact类：

import java.util.*;
import java.io.*;
import java.lang.*;


public class VectorofContact {

   Contact c = new Contact(); 
   private int size, capacity;
   private Contact [] addressBook; // naming the vector
   private Scanner fin;
   private PrintWriter fout;

   public VectorofContact()
   {
      addressBook = new Contact[12]; //12 cells
      size = 0; // actual number of things in the cells
      capacity = 12; //the amount of things the vector can hold
   }

   public void readInitialFromFile()
   {
       try
       {
           fin = new Scanner(new File("contacts.txt"));
       }
       catch (FileNotFoundException e)
       {
           System.out.println("Can't read from file");
       }
      while(fin.hasNext())
      {
         for(int i = 0; i < size; i++)
         {
            String[] split= fin.nextLine().split(":");
            String name = split[0];
            long phoneNumber = Long.parseLong(split[1]);
            String comment = split[2];
            name = addressBook[0].getName();
            phoneNumber = addressBook[1].getphoneNumber();
            comment = addressBook[2].getComment();
         }      
      }  
   } 

   public void deleteContact(String nM)
   {
      for(int i=0; i< size; i++)
      {
         if(addressBook[i].getName().equals(nM)) //delete the name the user wants to delete
         {
              addressBook[i] = addressBook[size - 1];
              size --; //since something got deleted, size is decremented
              return;
         }  
      }
   }

   public void showByComment(String cM)
   {
      for(int i=0; i < size; i++)
      {
         if(addressBook[i].getComment().equals(cM))//reading the input from user
         {
            System.out.println(addressBook[size]);
         }
      }
   }

   public void showByName(String nM)
   {
      for(int i=0; i<size; i++)
      {
         if(addressBook[i].getName().equals(nM))
         {
            System.out.println(addressBook[size]);
         }
      }
   }

   public void save() 
   {
      try 
      {
         fout = new PrintWriter("contacts.txt");
      }
      catch (FileNotFoundException e)
      {
         System.out.println("Can not write file?!?");
         return;
      }
         for (int i=0; i<size; i++)
         { 
            fout.print(addressBook[i] + "\t");
         }
         fout.println();

      fout.close();
   }


}

这是我的Driver2类

import java.util.*;
import java.io.File;

public class Driver2
{
   public static void main(String[] args)
   {
      VectorofContact v = new VectorofContact();
      //orderedVectorofContact oV = new orderedVectorofContact();
      File f = new File("contacts.txt");

      if(f.exists())
      {
         v.readInitialFromFile("contacts");
      }

      Scanner input = new Scanner(System.in);
      String commands; 
      boolean quit; //the quit command
      boolean noContact; //if the conact doesn't exist in array.

      quit = false;
      noContact = false; 

      System.out.println("Welcome to Address Book");
      System.out.println("Would you like to use a Vector or an Ordered Vector?");
      while(!noContact)
      {
         System.out.println(v.toString());
         commands = input.next();
         switch(commands)
         {
            case "Vector" : System.out.println("Please enter your command: ");
                                                                              break;
            case "Ordered Vector" : System.out.println("Please enter your" 
                                                + " command: ");              break;
            case "add": System.out.println("Name?");
                        //oV.addContact(input.nextLine());
                        System.out.println("Phone number?");
                        //oV.addContact(input.nextLong());
                        System.out.println("Comment?quit");
                        //oV.addContact(input.nextLine());                      
                                                                              break;

            case "Find name": System.out.print("What name would you like"
                                          + " to search?");
                              v.showByName(input.nextLine());                 break;

            case "Find comment": System.out.println("Please enter the "
                                          + " comment you wish to search: ");
                                  v.showByComment(input.nextLine());          break;

            case "remove" : System.out.println("What would you like to remove?");
                            System.out.println("Removed: " );
                                        v.deleteContact(input.nextLine()); break;

            case "quit" : quit = true;
                          System.out.println("Writing contacts.txt");
                          v.save();                                           break;

            default: break;                                       
         }
         if(noContact)
         {
            System.out.println("Contact does not extist/ has not been added");
         }   
      }
   }
}

“if语句”是吐出错误的那个。但它与我的VectorofContact类中的readInitialFromFile方法有关。

Answer 1

您的readInitialFromFile方法有此签名：

public void readInitialFromFile() { /* implementation*/ }

这意味着它接受无参数，而您尝试在此处传递一个String参数：

if(f.exists())
{
    v.readInitialFromFile("contacts");
}

删除"contacts"并进行编译。另一种解决方案是修改readInitialFromFile的签名以接受一个String参数：

public void readInitialFromFile(String str) { /* implementation*/ }

Answer 2

   public void readInitialFromFile()

此声明表明readInitialFromFile不带参数。但是你给了它一个：

   v.readInitialFromFile("contacts");

这让糟糕的编译器感到困惑。由于您的readInitialFromFile方法看起来像

public void readInitialFromFile()
{
    try
    {
        fin = new Scanner(new File("contacts.txt"));
    }
    ...

看起来您正在尝试设置它，以便您可以传入任何字符串作为文件名，而不仅仅是"contacts"。因此，您可能希望向方法添加String name参数（或任何您想要的参数名称），然后在方法体中使用new File时使用该参数。

一般来说，“实际和形式的参数列表长度不同”错误意味着它所说的内容。形式参数列表（或参数列表）是指您在编写方法时声明的参数;在你的情况下，这是0参数。实际参数（参数）列表是指调用方法时给出的参数数量，在您的示例中为1。

获得“实际和正式的参数列表长度不同”错误

2 个答案: