使用扫描仪从文件读取对象

Question

Am trying to read an object from a text file using scanner, but my problem is i cannot access the object's elements. Meaning i have stored an username and a password in the object and i want to check it with another username and password which the user will provide at run time.

Here is what i have done :

 //writing object to the file using printwriter 
    public void createLogin(String username,String password){

        libraryLogin_class logins=new libraryLogin_class(username,password);

        try{
            PrintWriter write=new PrintWriter("login.txt");
            write.print(logins);

           write.close();

        }catch(Exception e){}

    }

//This method is not fully implemented am currently stuck at this method

     public void checkLogin(String userName,String password)throws FileNotFoundException{

       File read=new File("login.txt");

       Scanner readFile=new Scanner(read);
     String loginObject;


      while(readFile.hasNext()){

          loginObject=(readFile.nextLine());

      //not implemented

      }


//class which creates an object with the default username and password

   public void login(){

        String username="shehan";
        String password="123";

        createLogin_class user=new createLogin_class();

        user.createLogin(username, password); //calls the creatLogin method and pass   the parameters

    }

So now my problem is how do i use the loginObject to check whether the object's username is equal to the username which the user provides?

Thank you for your time.

Answer 1

A PrintWriter has a print(Object) method as such

public void print(Object obj) {
    write(String.valueOf(obj));
}

So calling

write.print(logins);

will write the value of logins.toString() to your text file. You need to control that format. So if your toString() method is

public String toString() {
    return username + "," + password;
}

assuming you have fields username and password , you should read it as

while(readFile.hasNext()){
    libraryLogin_class login = new libraryLogin_class();

    loginObject = readFile.nextLine();
    String[] values = loginObject.split(",");
    login.setUsername(values[0]);
    login.setPassword(values[1]);
    // use login
} 

You would obviously want to validate what you're reading first.