如何修改我的信用卡验证器程序以仅检查我最后一个检查卡类型的函数中的有效数字？

问题描述

公共课程序{

// Global variables to be use in the whole program
public static int numOfInvalids = 0,visaNum=0 ; 



public static void main(String[] args) 
{
    
    Scanner userInput = new Scanner(system.in) ;
    

    System.out.println("How many credit card you want to check?");
    int numOfCredit = userInput.nextInt() ;
    
    int creditnumbers[] = new int[numOfCredit] ;
    
    for (int i = 0 ; i<numOfCredit ; i++)
    {
        System.out.println("Enter credit card number "+(i+1)+": ") ;
        String creditNumber = userInput.next() ;
        
        // checks if number is a credit number or not
        
        if (creditNumber.length()<16 || creditNumber.length()>19)            
        {
            System.out.println("Not a credit card number!") ;
            prog.numOfInvalids ++ ;  // count number of invalid card numbers
            
            System.out.println();
            continue ;
        }
        
        checkValid(creditNumber);
        checkType(creditNumber) ;
        // calls function 

    }
    System.out.println("Number of invalid: "+prog.numOfInvalids) ;
    System.out.println("Number of visa credit card: "+prog.visaNum) ;
    
    
}



private static boolean checkValid(String cardNumber)        // function to check if card number is valid or not 
{
    int cardlength = cardNumber.length();
    int evenSum = 0,oddSum = 0,sum;
    
    
    for (int i = cardlength - 1; i >= 0; i--)  //looping from the right 
    {
        int digit = Character.getNumericValue(cardNumber.charat(i));  // Character.getNumericValue = convert char to integer
        
        if (i % 2 == 0)  // taking every 2nd digits from the right e.g 2nd..4th..6th..8th etc.
        {
            int multiplyByTwo = digit * 2;     // multiply each 2nd digits by 2
            
            if (multiplyByTwo > 9)  // Add two digits to handle cases that make two digits after doubling  e.g (6 * 2 = 12) = 1 + 2
            {
                
                String doubleDigits = String.valueOf(multiplyByTwo);  // convert double digit to String for use of charat function
                multiplyByTwo = Character.getNumericValue(doubleDigits.charat(0)) + Character.getNumericValue(doubleDigits.charat(1));   //convert each character to integer and add them together
            }
            
            evenSum += multiplyByTwo;  // add product digits together
            
            } 
        
        else 
        {
            oddSum += digit;      // Add sum of digits that weren’t multiplied by 2
        }
    }
    
    sum = evenSum + oddSum;   //Adding both sums together
    
    if (sum % 10 == 0)       //if sum is multiple of 10,it is valid 

    {
        
        System.out.println("valid card");
        System.out.println();
        return true;    
       
    } 
    
    else
    {
        System.out.println("invalid card") ; 
        prog.numOfInvalids ++ ; // count the number of invalid card numbers
        System.out.println();
        return false;
        
    }
}

private static boolean checkType(String cardNumber) // function to check card type 
{
    


    if ( (cardNumber.charat(0)=='4') && cardNumber.length()==13 || cardNumber.length()==16 )  //checking first character and length of card number
            {
                System.out.println("VISA");
                visaNum ++ ; // counting number of visa cards 
                return true;    
            } 
            
            else
            {
           
                return false;
            }

} }

我只想从第一个函数“check Valid”到最后一个函数“Check Type”检查有效卡的卡类型

有什么办法可以保存第一个函数中的有效数字并在“检查类型”函数中使用它们？

我只想从第一个函数“check Valid”到最后一个函数“Check Type”检查有效卡的卡类型

有什么办法可以保存第一个函数中的有效数字并在“检查类型”函数中使用它们？

解决方法

基于问题的假设

1. 只需要为有效卡推断卡类型
2. 无法更改函数返回类型

可能的方法

1. 对 if 的响应添加 checkValid 检查，如果为真，则调用 checkType

   if (checkValid(creditNumber) {
        checkType(creditNumber);
   }

建议

1. 无论采用哪种解决方案，请在编码和提问时改进格式，因为这将有助于其他人更好地理解问题。