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（。）。如果用户省略或者，您的程序必须通知用户所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为止地址。当用户输入有效的电子邮件地址时，请继续执行该程序的其余部分。 -我们应该为此使用一个循环，但是我不确定该使用哪个或如何设置它。我在考虑使用while循环吗？我们还不能使用正则表达式方法，因为我们还没有学到它。

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。当您知道需要重复多少次操作时，最好使用for循环，但是使用while循环可以重复未知次数。它可以运行0到很多次。

关于while循环的条件，您只想检查电子邮件地址是否无效。因此，请检查!emailAddress.contains("@")以查看它是否不包含@，如果它不包含!emailAddress.contains(".")，请检查.。

您可以使用||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

类似的事情应该起作用：

// 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 
// ...

使用循环来确定电子邮件地址是否包含2个字符

2 个答案: