This validator is best used to validate a specific property of the row - either about a specific element or information about the array itself.

An empty or null first row is considered invalid.

As with all row validators the assumption is you have control of the data and have skipped any initial empty lines AND that your validator checks the size or handles the IndexOutOfBoundsException.

There are several examples coded in the RowFunctionValidatorTest but here are a couple to give you the idea of the flexibility this validator offers.

private static final String[] GOOD_ROW = {"8675309", "Firstname", "M", "Lastname", "Dec 06, 1951"};
    private static final String[] BAD_ROW = {"not a number", "not capitialized", "not an initial", "Not Single word", "12/06/51"};
    private static final String[] LONG_ROW = {"8675309", "Firstname", "M", "Lastname", "Dec 06, 1951", "More data"};
    private static final String[] SHORT_ROW = {"8675309", "Firstname", "Lastname", "Dec 06, 1951"};

    private static final Function<String[], Boolean> THIRD_ELEMENT_IS_MIDDLE_INITIAL = (x) -> {
        return x.length > 2 && x[2].matches("^[A-Z]$");
    };

    private static final Function<String[], Boolean> ROW_MUST_HAVE_FIVE_ELEMENTS = (x) -> {
        return (x.length == 5);
    };

@Test
@DisplayName("Simple test to show checking an middle initial")
public void thirdElementIsMiddleInitial() {
        validator = new RowFunctionValidator(THIRD_ELEMENT_IS_MIDDLE_INITIAL, "The third element must be the middle initial.");

        assertTrue(validator.isValid(GOOD_ROW));
        assertFalse(validator.isValid(BAD_ROW));
    }

@Test
@DisplayName("The row must have a specific number of elements in order to be valid.")
public void numberOfElementsInARow() {
        validator = new RowFunctionValidator(ROW_MUST_HAVE_FIVE_ELEMENTS, "A Row can have only five elements.");

        assertTrue(validator.isValid(GOOD_ROW));
        assertFalse(validator.isValid(LONG_ROW));
        assertFalse(validator.isValid(SHORT_ROW));
    }