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Edwin Torres
Edwin Torres

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Algorithm Development: Verifying a Social Security Number

A person's social security number is in a specific format:

nnn-nn-nnnn

For example, this is an example of a valid social security number:

111-22-3333

Note that this is just a fictitious example for this article.

An algorithm to verify that a social security number is valid starts with rules:

  • The social security number must be a string.
  • The string must be of length 11.
  • There are hyphen (-) characters in the 3rd and 6th positions of the string (starting with position 0).
  • All other characters in the string must be digits in the range 0 to 9.

Here are some sample social security numbers that fail to meet these requirements:

  • 111223333 - length is not 11 and hyphens are missing
  • 11-1223-333 - hyphens are in the wrong positions
  • 111-aa-3333 - non-numeric characters are in positions 4 and 5
  • 111-22-333 - length is not 11

Here is one possible algorithm to verify the format of a social security number:

  1. Input the social security number as a string value.
  2. Check the length of the social security number.
    • If the length is not equal to 11, output a message that the social security number is invalid and exit the program.
    • Otherwise, continue to the next step.
  3. Check that positions 3 and 6 of the social security number are hyphen (-) characters. One way to do this is with the Java String method charAt() .
    • If one or both of the positions is not the hyphen (-) character, output a message that the social security number is invalid and exit the program.
    • Otherwise, continue to the next step.
  4. Check that all other positions in the social security number are numbers in the range 0 - 9. One way to do this is with the Java String method isDigit().
    • If at least one of these characters is not a digit, output a message that the social security number is invalid and exit the program.
    • Otherwise, output a message that the social security number is valid.

This just one possible algorithm for verifying the format of a social security number. There are other ways to do this. But algorithm development is the focus here. Develop a solid algorithm before writing code. Then it is just a matter of translating the algorithm into real Java statements.

Thanks for reading. 😃

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