[Solved] Using String#contains() and String#indexOf() to locate a date format String in a comma separated list finds incorrect matches [closed]

Question

Currently you are not searching for a single date format in a list of date formats, you are searching for a date format String within a single String that contains multiple comma separated date formats.

Since that String starts with "dd/MM/yyyy", which contains "dd/MM/yy", both contains and indexOf find a match (which, given your requirements, is a false positive).

In order to search for full date formats only (in your comma separated list), you should split your input String into a List<String>, and run contains of that List:

Arrays.asList(validDateFormats.split(",")).contains("dd/MM/yy")

validDateFormats.split(",") splits the input String into a String array (using the comma as a separator). Arrays.asList creates a List<String> backed by that array, which allows you to run List‘s contains method to search for the "dd/MM/yy" date format. This will return false as expected.

Accepted Answer

Currently you are not searching for a single date format in a list of date formats, you are searching for a date format String within a single String that contains multiple comma separated date formats.

Since that String starts with "dd/MM/yyyy", which contains "dd/MM/yy", both contains and indexOf find a match (which, given your requirements, is a false positive).

In order to search for full date formats only (in your comma separated list), you should split your input String into a List<String>, and run contains of that List:

Arrays.asList(validDateFormats.split(",")).contains("dd/MM/yy")

validDateFormats.split(",") splits the input String into a String array (using the comma as a separator). Arrays.asList creates a List<String> backed by that array, which allows you to run List‘s contains method to search for the "dd/MM/yy" date format. This will return false as expected.