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我正在编写一个具有用户名和密码输入的程序。我试图检查用户是否存在文件,如果用户在创建用户名和密码时输入已存在的用户名。
.exists方法不起作用,我无法弄明白。错误找不到符号回来。我改变了一些东西,把事情搞砸了,并把它归结为一个错误。尝试使用循环以及if语句,但使用if只能让我犯一个错误。任何帮助都会很棒。
import java.util.Scanner;
import java.io.*;
class UserData
{
public static void main ( String[] args ) throws IOException
{
Scanner kb = new Scanner(System.in);
System.out.println("Do you have an account? Yes or No: ");
String answer = kb.next().trim();
if ((answer.startsWith("N")) || (answer.startsWith("n")))
{
System.out.println("Create user name: ");
String user = kb.next().trim();
String fileName = user + ".txt";
FileWriter userData = new FileWriter(fileName);
if (userData.exists())
{
System.out.println("User already exists");
System.out.println("Create user name: ");
user = kb.next().trim();
fileName = user + ".txt";
userData = new FileWriter(fileName);
}
System.out.println("Create Password: ");
String ps = kb.next().trim();
userData.write(user + " ");
userData.write(ps);
userData.close();
}
else if ((answer.startsWith("Y")) || (answer.startsWith("y")))
{
System.out.println("Enter user name: ");
String user = kb.next().trim();
System.out.println("Enter Password: ");
String ps = kb.next().trim();
String fileName = user + ".txt";
Scanner inFile = new Scanner(new File(fileName));
String userName = inFile.next();
String password = inFile.next();
// If ((userName != user) || (password != ps))
// {
// System.out.println("User Not Found");
// System.out.println("Enter user name: ");
// String user = kb.next().trim();
//
// System.out.println("Enter Password: ");
// String ps = kb.next().trim();
//
// String fileName = user + ".txt";
// Scanner inFile = new Scanner(new File(fileName));
//
// String userName = inFile.next();
// String password = inFile.next();
// }
// else
// {
System.out.println("User Found");
// }
}
}}
答案 0 :(得分:3)
这里有编译错误:
FileWriter userData = new FileWriter(fileName);
if (userData.exists())
将其更改为:
File userDataFile = new File(fileName);
if (userDataFile.exists())
当然:
FileWriter userData = new FileWriter(userDataFile);
userData.write(user + " ");
userData.write(ps);
userData.close();
如果文件不存在,您可能正在查找错误的目录。尝试添加:
System.out.println(new File(fileName).getAbsolutePath());
并检查打印路径上的文件是否可用。