使用循环确定电子邮件地址是否包含 2 个字符

Question

检查电子邮件地址是否有效。有效的电子邮件地址应同时包含 at 符号 (@) 或点 (.)。如果用户省略了其中任何一个，您的程序必须通知用户提供的电子邮件不正确，并提示用户重新输入电子邮件地址。继续重复此步骤，直到用户提供有效的电子邮件地址。当用户输入有效的电子邮件地址时，继续执行程序的其余部分。- 我们应该为此使用循环，但我不确定使用哪个或如何设置它。我在考虑使用while循环？我们不能使用我在这里看到人们使用的正则表达式方法，因为我们还没有学到这一点。This is the code that we have to update(we are now supposed to use a loop to continue asking the user for email address until both characters are used, instead of exiting the program):if(emailAddress.contains("@")){     //prompt user for major & classification code    System.out.print("\nPleast enter two characters (Character #1: Major Code and Character #2: Classification Code): ");    } else{     //exit program if no '@' symbol in email address    System.out.print("\nYou have entered an invalid email address.");    System.out.println("\n\nGoodbye!");    System.exit(0);}

Answer 1

我建议使用while循环。当for您知道需要重复操作多少次时，循环是最好的，但while循环适用于重复未知次数。它可以运行 0 到多次。

至于您的while循环条件，您只想检查电子邮件地址是否无效。因此，请检查!emailAddress.contains("@")它是否不包含@，!emailAddress.contains(".")如果不包含.。

您可以使用||来查看任一条件是否为真。

// Prompt the user

System.out.println("Please enter an email address");

String emailAddress =  // read in their email adress 

while(!emailAddress.contains("@") || !emailAddress.contains(".")) {

    System.out.println("You have entered an invalid email address, please enter another.");

    emailAddress = // read in their email address again

}

// Email address now contains "@" and "."

Answer 2

像这样的东西应该工作：

// While email does not contain the two characters..

// Keep asking the user to enter the correct email.

while(!emailAddress.contains("@") || !emailAddress.contains(".")){ 

    System.out.print("\nYou have entered an invalid email address.");

    // Add line of code here to ask for email address.

    // Update emailAddress of course

}

//prompt user for major & classification code

System.out.print("\nPleast enter two characters (Character #1: Major Code and Character #2: Classification 

// ...