java - 需要一个不满足的 if 语句来转到代码开头

Question

我正在尝试设置一些 if 语句，以确保用户输入不会超出我设置的范围(如果我希望 if 语句将它们返回到主代码的开头)。

String animal = JOptionPane.showInputDialog("Enter In Animal Name"); // Asking for user to enter a animal
String fruit = JOptionPane.showInputDialog("Enter In A Fruit Name"); // Asking user to enter a fruit
int days = Integer.parseInt(JOptionPane.showInputDialog("Enter In How Many Days Between 1 And 10"));
// Above integer is asking the user to enter the amount of days.

// Below if statements are basically error checking to ensure the user stays between the
// range asked for when they are asked to enter in days between 1 and 10.

if (days <= 0) { // Ensures that negative numbers cannot be entered.
    JOptionPane.showMessageDialog(null, "Error, Please enter a number between 1 and 10");
    return;
}
if (days >= 10) { // Ensures nothing over 10 can be entered.
    JOptionPane.showMessageDialog(null, "Error, Please enter a number between 1 and 10");
    return;
}

如果 if 语句说它是一个错误，它应该返回要求他们重新输入天数

Answer 1

使用 do-while 循环，该循环将至少执行一次，如果 days 不满足条件，则每次循环返回。

public static void main(String[] args) 
{
    do {
        //Your other code
        String animal = JOptionPane.showInputDialog("Enter In Animal Name"); // Asking for user to enter a animal
        String fruit = JOptionPane.showInputDialog("Enter In A Fruit Name"); // Asking user to enter a fruit

        int days = askForInput();

        if (days <= 0 || days >= 10) { // Ensures that negative numbers cannot be entered.
            JOptionPane.showMessageDialog(null, "Error, Please enter a number between 1 and 10");
        }

    } while (days <= 0 || days >= 10);
}

//Pass whatever parameters you might need
public static int askForInput() {
    int days = Integer.parseInt(JOptionPane.showInputDialog("Enter In How Many Days Between 1 And 10"));
    //Any other code you want
    return days;
}

我还将它提取到一个方法中，这可能是不必要的，但如果需要，它可以让您添加更多功能。

如果您不想每次都询问该问题，也可以将 animal 或 fruit 移到 do 之外。