Welcome to the Java Programming Forums

The professional, friendly Java community. 21,500 members and growing!

The Java Programming Forums are a community of Java programmers from all around the World. Our members have a wide range of skills and they all have one thing in common: A passion to learn and code Java. We invite beginner Java programmers right through to Java professionals to post here and share your knowledge. Become a part of the community, help others, expand your knowledge of Java and enjoy talking with like minded people. Registration is quick and best of all free. We look forward to meeting you.

>> REGISTER NOW TO START POSTING

1. ## Credit card help

Can someone help me with this?

The last digit of a credit card number is the check digit, which protects against transcription errors such as an error in a single digit or switching two digits. the following method is used to verify actual digit card numbers but for simplicity, we will describe it for numbers with 8 digits instead of 16.
--> Starting from the rightmost digit, form the sum of every other digit. For example, if the credit card number is 4358 9795, then you form the sum 5+7+8+3=23
--> Double each of the digits that were not included in the preceding step. Add all digits of the resulting numbers. For example, with the number given above, doubling the digits, starting with the next-to-last one yields 18 18 10 8. Adding all digits in these values yields 1+8+1+8+1+0+8=27
--> Add the sums of of the two preceding steps. If the last digit of the result is 0, the number is valid. IN our case, 23+27=50, so the number is valid

Write a program that implements this algorithm. The user should supply an 8 digit number, and you should print out whether the number is valid or not. If it is not valid, you should print the value of the check digit that would make it valid.

2. ## Re: Credit card help

What have you done so far?