unit testing - Test flat file content and format in Java -

i have send flat file external system. sample file content given below:

start 20150602 header 100.00usd product test1                    50.00usd product test2                    50.00usd footer 002 

this file should follow below guidelines:

first line - starts start, space, today's date in yyyymmdd header line - starts header, space, total amount of first, second, third etc products 2 decimal points, currency first product - starts product, space, product name left aligned total 25 characters, amount 2 decimal points, currency more products similar first product, number of products dynamic footer - starts footer, space, total number of products 3 digits 

this format has been given external system vendor in excel.

can of suggest better testing strategy in these case? there tools test file content , format?

in situations this, prefer explore options starting simple approach, based on elementary java features. here, each line may described regular expression:

start (\d{8}) header (\d+\.\d{2})(\w{3}) product (.{25}) (\d+\.\d{2})(\w{3}) footer (\d{3}) 

you may not need parentheses if don't need extract , check values. otoh, add list of strings, providing names these fields can entered map.

you can add minimum , maximum repeat count each line, let write simple logic iterate through lines of file.

these might factory method calls of above defined couple of lines:

linedef.create( "header (\\d+\\.\\d{2})(\\w{3})", 1, 1,                 "totalamount", "totalcurrency" );  linedef.create( "product (.{25}) (\\d+\\.\\d{2})(\\w{3})", 1, 999,                "name", "amount", "currency" );