密码屏蔽不会在需要时终止程序

Question

我开发了以下应用程序，其中我需要屏蔽 PIN 并在用户输入错误 PIN 三次后终止程序。但是，仅当我在开始时关闭 stopThread （我在下面的代码中对其进行了注释）时，程序才会终止，但是当我这样做时，所有三种机会都不会发生密码屏蔽。但是，当我在显示登录成功屏幕之前关闭 stopThread 时，程序不会终止。我需要使用ctrl+c来结束程序。

非常感谢任何帮助。

boolean stopThread = false;
boolean hideInput = false;
boolean shortMomentGone = false;
public static double userBal=0.0D;

public void run(){
    try{
        sleep(500);
    } catch(InterruptedException e){
    }
    shortMomentGone = true;
    while(!stopThread){
        if(hideInput){
            System.out.print("\b*");
        }
        try{
            sleep(1);
        } catch(InterruptedException e){
        }
    }
}

public static final int NB_OF_TRIES = 3;        

public void validatePin(){
    BankAccount getAll=new BankAccount();
String pin="";
    getAll.Login();
    Login hideThread =new Login();
    hideThread.start();
    BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
    try{    
    do{

        } while(hideThread.shortMomentGone == false  );          
    // Now the hide thread should begin to overwrite any input with "*"
        hideThread.hideInput = true;            // Read the PIN
        System.out.println("\nPIN:");

    boolean pinMatch = false;
        int i = 0;

    while(!pinMatch && i < NB_OF_TRIES) {
        hideThread.hideInput = true;
        pin = in.readLine();
    i++;
        //hideThread.stopThread = true;       //Program terminates after third attempt 
                                              //PIN masking is stopped, if uncommented
        System.out.print("\b \b");        
        if(pin.equals(" ")){
    System.out.println("Please do not leave unnecessary spaces!");
    getAll.Login();
    }else if(pin.equals("")){
    System.out.println("Please do not press the enter key without entering the PIN!");
        getAll.Login();
    }

    FileInputStream fileinputstream = new FileInputStream(".\\AccountInfo.txt");
        DataInputStream datainputstream = new DataInputStream(fileinputstream);
        BufferedReader bufferedreader1 = new BufferedReader(new InputStreamReader(datainputstream));

    do
        {
            String s1;
            if((s1 = bufferedreader1.readLine()) == null)
            {
                break;
            }
            if(s1.trim().charAt(0) != '#')
            {
                String as[] = s1.split(" ");
                if(pin.equals(as[0]))
                {          
                    System.out.println("You have login!");
                    String s2 = as[2];
                    userBal = Double.parseDouble(s2);                       
                    getAll.balance = userBal;
                hideThread.stopThread = true;
                    getAll.MainMenu();
        System.exit(0);
                }else if(pin != as[0]){
        System.out.println("Invalid PIN!");
        getAll.Login();           
        System.out.println("\n NOTE :- You are only allowed to enter the PIN THREE times. The number of tries remaining before your card is blacklisted are "+i + "\n Please re-enter your PIN");
                }
            }
        } while(true);
        datainputstream.close();    
    }//End of While Loop

    }catch(Exception exception)
    {
        System.err.println((new StringBuilder()).append("Error: ").append(exception.getMessage()).toString());
    }//End of try-catch block    
}

Answer 1

java.io.Console中有一个readPassword()方法，使用它。为什么你需要一个单独的线程？这让一切变得太复杂了。

关于你的问题为什么这不关闭：如果你不这样做，Java可能会将 while(isTrue){} 优化为 if(isTrue) { while(true) { } }不设置 isTrue volatile 或同步对 isTrue (getter/setter) 的访问。这种优化称为提升，并在《Effective Java SE》第 66 项中进行了解释。

这里有一篇文章准确地解释了您的问题：回显 * 而不是空白。
http://java.sun.com/developer/technicalArticles/Security/pwordmask/
他们也在走复杂的路，但它有效。我更喜欢空白而不是星号，因为这是更简单的方法。不回显 * 是 *nix 标准据我所知。

Answer 2

实际上，在我分析了它之后，我意识到系统不会终止的原因是因为它没有保存在正确的位置。因此，解决方案是在 while 循环关闭后立即结束程序，然后一切都会正常工作。

        } while(true);
        datainputstream.close(); 
 }//End of While Loop
     System.exit(0);  // After the system is closed the program would terminate after the third attempt
    }catch(Exception exception)
    {
        System.err.println((new StringBuilder()).append("Error: ").append(exception.getMessage()).toString());
    }//End of try-catch block