如何从Java中的用户输入获取int的长度

debugcn 发表于 Dev

用户名

我正在尝试获取用户输入的字符的长度。如果用户输入的字符串长度小于5或大于5，则应该说“输入有效的5位数字”。如果长度为5，那么我希望它继续下一个问题，但是由于某种原因，它无法正常工作。谢谢！

package Hw;
import java.util.Scanner;
public class Library {

public static void main(String[] args) {

int  cardnumber = 0;
int age;
int item = 0;
int overdue = 0;

int fine = item * overdue;

int length = length(Integer.toString(cardnumber));

Scanner Keyboard = new Scanner (System.in);



System.out.println("Enter Card Number: ");
cardnumber = Keyboard.nextInt();
System.out.println("Enter Age: ");
        age = Keyboard.nextInt();
        System.out.println("Enter Item Type (Book = 1, Magazine = 2, Dvd = 3): ");
        item = Keyboard.nextInt();
        System.out.println("Enter The Amount Of Days The Item Has Been Overdue");
overdue = Keyboard.nextInt();

if (length == 5)
{
System.out.println(cardnumber);
}
if (length > 5 || length < 5)
{
System.out.println("Enter A Valid 5 Digit Number");
}



if (item == 1)
{
fine = (int) (overdue * 0.50);
}

else if (item == 2)
        {
            fine = (int) (overdue * 0.25);
        }

    else if (item == 3)
        {
        fine = (int) (overdue * 1.50);
        }



if (age > 5 || age < 18)
{
fine = (int) 1.00;
}


if (age > 70)
{
fine = 0;
}


else if(age > 18 || age < 70)
{

if(overdue < 5)
System.out.println("Days Overdue "+ overdue);
}

else
{
fine = (int) 5.00;
}


/*else if (age < 6 || age > 17)
{
fine = (int) 1.00;
}
*/



System.out.println("Card Number "+ cardnumber);



System.out.println("Age "+ age);

//  System.out.println("Days overdue "+ overdue);

System.out.println("Fine "+ fine);

//  System.out.println("Fine adjustment reason "+ )


if(item == 1)
{
System.out.println("item Book");
}

else if(item == 2)
{
System.out.println("item Magazine");
}

else if(item == 3)
{
System.out.println("item Dvd");
}

else if(item <1 || item >3)
{
System.out.println("Invalid Information");
}   
}

private static int length(String string) {
// TODO Auto-generated method stub
return 0;
}
}

红色的

主要概念应该是使用String而不是Integer，通过这种方法，检查用户的输入长度更加容易和快捷。

我建议更改代码，如下所示：更改该行：

int length = length(Integer.toString(cardnumber));

至：

String length = Integer.toString(cardnumber);

另一个更改是以下几行：

if (length == 5)
{
System.out.println(cardnumber);
} 
if (length > 5 || length < 5)
{
System.out.println("Enter A Valid 5 Digit Number");
}

应替换为：

while(length != 5) {
    System.out.println("Enter A Valid 5 Digit Number");
    cardnumber = Keyboard.nextInt();
    length = Integer.toString(cardnumber);
}

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