Question

我创建了一个Java程序，它读取每个名称都有两个字符串的.txt文件。

Rob Junior

鲍比凯利

当它读取它并且找不到相关名称时，它将显示一个对话框错误消息。我遇到的问题是程序正在读取每一行，如果它不匹配，将显示每行的错误消息。这是我的代码片段：

  Scanner fileScan = new Scanner (new File("1.txt"));
  while (fileScan.hasNextLine()){
      String input = fileScan.nextLine();
      String Username = input.substring(0,input.indexOf(' '));
      String Password = input.substring(input.indexOf(' '),input.length());

      if (Username.equals(inputusername) || (Password.equals(inputpassword)))
      {
          getContentPane().removeAll();
          getContentPane().add(panel3);//Adding to content pane, not to Frame
          repaint();
          printAll(getGraphics());
      } 
      else {
          JOptionPane.showMessageDialog(null,
                "Invalid password. Try again.",
                "Error Message",
                JOptionPane.ERROR_MESSAGE);
      }
  }

inputusername和inputpassword是读取程序中文本字段的字符串。我知道我应该使用除了while循环之外的东西，但似乎无法将它拼凑在一起。

Answer 1

您要做的是移动检查以查看密码是否不在while循环外的文件中。以下代码通过将临时变量设置为false，然后在找到用户名和密码组合时将其设置为true来执行此操作。否则，它仍为false，在检查文件后，我们显示对话框错误。

  Scanner fileScan = new Scanner (new File("1.txt"));
  boolean found = false; // added this variable
  while (fileScan.hasNextLine()) {
    String input = fileScan.nextLine();
    String Username = input.substring(0,input.indexOf(' '));
    String Password = input.substring(input.indexOf(' '),input.length());

    if (Username.equals(inputusername) || (Password.equals(inputpassword))) {
      found = true; // added this to set found
      getContentPane().removeAll();
      getContentPane().add(panel3);//Adding to content pane, not to Frame
      repaint();
      printAll(getGraphics());
    } // removed the else statement
  }

  if(!found) { // added the contents of the previously existing else statement here, outside the while
    JOptionPane.showMessageDialog(null,
      "Invalid password. Try again.",
      "Error Message",
      JOptionPane.ERROR_MESSAGE);
  }

Answer 2

试试这个：

    Scanner fileScan = new Scanner(new File("1.txt"));
    boolean founduser = false;
    while (fileScan.hasNextLine()) {
        String input = fileScan.nextLine();
        String Username = input.substring(0, input.indexOf(' '));
        String Password = input.substring(input.indexOf(' '), input.length());

        if (Username.equals(inputusername) && (Password.equals(inputpassword))) {
            founduser = true;
            break;
        }
    }

    if (founduser) {
        getContentPane().removeAll();
        getContentPane().add(panel3);// Adding to content pane, not to Frame
        repaint();
        printAll(getGraphics());
    }

    else {
        JOptionPane.showMessageDialog(null, "Invalid password. Try again.", "Error Message",
                JOptionPane.ERROR_MESSAGE);
    }

Answer 3

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;


public class FileReading {
    public static void main(String args[]) throws FileNotFoundException{
      Scanner fileScan = new Scanner (new File("test.txt"));
      boolean found = false; // added this variable
      while (fileScan.hasNextLine()) {
        String input = fileScan.nextLine();
        String Username = input.substring(0,input.indexOf(' '));
        String Password = input.substring(input.indexOf(' ')+1,input.length());


        if ((Username.equals("pawan")) && (Password.equals("kalyan"))) {
          found = true; // added this to set found
          System.out.println("Success");

        } 
      }

      if(!found) { 
        System.out.println("failed");
      }
    }
}

Answer 4

这是您问题的解决方案

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

public class Credentials {

public static void main(String[] args) throws Exception {
    InputStreamReader isr = new InputStreamReader(System.in);
    BufferedReader br = new BufferedReader(isr);
    System.out.println("Enter user name");
    String inputUser = br.readLine();
    System.out.println("Enter Password");
    String inputPassword = br.readLine();

    Credentials c =new Credentials();
    c.readPassword(inputUser,inputPassword );
}

void readPassword(String inputUser,String inputPassword) throws Exception {
   Scanner scr = new Scanner(new File("password.txt"));
   boolean flag=false;
   while(scr.hasNextLine()){
   String line = scr.nextLine();
   String username= line.substring(0,line.indexOf(' '));
   String password =line.substring(line.indexOf(' ')+1,line.length());
       System.out.println(username+","+password);

   if(inputUser.endsWith(username) && inputPassword.equals(password) ){
       System.out.println("Valid user");
       flag=true;
       break;
   }

   }
   if(!flag){
       System.out.println("invalid user");
   }
}

}

文件检查用户名和密码

4 个答案: