Re-prompting the user for data input with an if statement

问题

I'm trying to prompt for a first/last name in this code, but I cannot figure out how to re-prompt a user for the name if they forget to fill out the field. Right now if my code does not get any input and the user clicks onwards, I have it so a message box will pop up and then the program will close. I want to be able to just re-prompt for the exact same step without it getting all out of order.

This is what I have so far:

public void getValues(){
    firstName = JOptionPane.showInputDialog(null, "Please enter employee's first name");

    if (firstName.equals("")){

        JOptionPane.showMessageDialog(null,"Please enter a first name, next time.");
        System.exit(-1);
    } else {

    lastName = JOptionPane.showInputDialog(null, "Please enter employee's last name");

    if (lastName.equals("")){

        JOptionPane.showMessageDialog(null,"Please enter a last name, next time.");
        System.exit(-1);
    } else {

Thank you.

回答1:

Use a while loop where necessary until you get the input you want.

Here's a snippet.

String firstname = JOptionPane.showInputDialog(null, "Name?");
while(firstname.equals("")) {
    firstname = JOptionPane.showInputDialog(null, "You need to enter a first name!);
}

回答2:

You can use a while statement to continuously ask the user for input until the input is valid.

Ex:

while((firstName = JOptionPane.showInputDialog(null, "Your Message")).equals("")){
    JOptionPane.showMessageDialog(null, "That name isn't valid!");
}

回答3:

You can do something like this:

do {
    firstName = JOptionPane.showInputDialog(null, "Please enter employee's first name");
} while (firstName != null && firstName.equals(""));
if (firstName == null) {
    // user canceled
}

来源：https://stackoverflow.com/questions/8965839/re-prompting-the-user-for-data-input-with-an-if-statement

标签

java

validation

if-statement

joptionpane