java - java代码中执行两个if语句

Question

我目前正在尝试对员工登录表单进行验证。但我在验证输出中意识到，每当我在用户名文本字段中输入值时，它仍然会弹出消息“请输入您的用户名”，然后弹出“无效凭据”消息框。下面是我的代码:

 String username = usernameTxt.getText();
    String password = passwordTxt.getText();


    if  (username.contains(""))
  {
        JOptionPane.showMessageDialog(null,"Please Enter Your Username Credentials.");
    }
    else  if (password.contains (""))
  {
        JOptionPane.showMessageDialog(null,"Please Enter Your Password Credentials.");
    } 
   else if (password.contains ("") && (username.contains("")))
  {
        JOptionPane.showMessageDialog(null,"Please Enter Your Login Credentials.");
    }
   if ((username.contains("staff") && password.contains ("pass")))

    {
        JOptionPane.showMessageDialog(null,"Login Successfull","Success",JOptionPane.INFORMATION_MESSAGE);
        passwordTxt.setText(null);
        usernameTxt.setText(null);
        staffdashboard sd = new staffdashboard();
        sd.setVisible(true);
        this.setVisible(false);   
    }    
    else  
    {
        JOptionPane.showMessageDialog(null,"Invalid Login Details","Login Error",JOptionPane.ERROR_MESSAGE);
        passwordTxt.setText(null);
        usernameTxt.setText(null);
    }

enter user message box invalid login details message box

我错过了什么以及如何停止表单一次输出 2 个消息框？

Answer 1

问题出在第一个 if 语句中:username.contains("")

每个字符串都包含空字符串。您应该将其替换为 if("".equals(username))

或者使用StringUtils.isBlank(username);

对于所有contains("")都一样