While only would match “a”, “b”, etc * matches “”, “a”, “aaa”, “kjh”, “dlfkajhsdflkajhd”, and everything you can monkey-type on your keyboards alphabetic keys. The star/asterisk immediately behind the brackets means “find what I just typed any amount of times”. * - Match anything with letters between “a” and “z” following each other, for zero or infinite amount of times. Let’s say for popular example that you want to validate a western style first name (just letters, for simplicity). So you might like the bracket-search you wrote earlier and want to re-use it for more than just one character. A very wide search, most likely not that useful all the time. *an would match any character, for zero or infinite amount of times, ending with an. If you need you can use quantifiers with it (explained more in detail pretty soon). The dot only matches one single character (but any type of it). It will match numbers, letters, question marks, and everything you can think of.an - Match anything that starts with something and then ends with “an”, like “!an”, “7an”, “zan”, “Ran”, “_an” and “[an”. (dot) placed outside of a bracket will work as the “anything”-character. You have now taught yourself about the square brackets, multiple alternatives in them, ranges, and the not-search.
a - Match anything that ends with “an” or “ag”, but must not start with “D” or “B”.Īn - Match anything *but* “Dan”, “Ean”, “Fan”, “Gan”, but "San" and "pan" is for example valid. These “not”-searches can also be used with multiple brackets, characters, and ranges. None of these two examples would allow empty first character, "an" would thus not be valid. an - Match anything that ends with "an" and starts with any character except "D", so “Dan” would not be valid, but "San", "Can" or "man" would.Īn - Same as above, but also “Ban” is one of the invalid matches. Some examples: an - Match “0an”, “1an”, “2an”, “3an” and so on all the way to “9an”.Īn - Match any “an” starting with a number or capital letter.Īn - Match any “an” starting with any number, lower case or capital letter. The Regex looks at each letter like an alternative to match against except when you add the dash, then it understands that the two surrounding characters and everything between them will be matched. Some examples: an - Match “Aan”, “Can” and “Dan”.Īn - Match “Aan”, “Ban”, “Can”, “Fan” and “Gan”.Īn - Match “Aan”, “Ban”, “Fan”, “Gan” and “Zan”. How about multiple ranges with mixed in single characters. We can make it more complex by adding more to our brackets. Some examples: an - Match “Aan”, “Ban”, “Can”, “Dan”, and all the way up to “Zan”. You specify a range by writing the first character, followed by a dash, and ending with the last character. These are especially handy when we need to validate against the alphabet or numbers. You can also advance your brackets with ranges. You can have multiple brackets in one string, like so: a - Matches “Dan” and “Ban”, and also “Dag” and “Bag”. Meaning it will not match the entire string "Dan", only one single character (probably not what you wanted). Matches single character “D”, or “a”, or “n”. Some examples: an - Matches “Dan”, not very useful.Īn - Matches “Dan” and “Ban” (first letter can be "D" or "B").Īn - Matches “Dan”, “Ban”, “Tan”, and “Pan”.ĭa - Matches “Dan” and “Dag” (last letter can be "n" or "g"). Everything you put inside these brackets are alternatives in place of one character. If you are searching for a name in a string but you’re not sure of the exact name you could use instead of that letter a square bracket. Square brackets match something that you kind of don’t know about a string you’re looking for.
Hello - Matches the word “Hello” in a string.īut the true power of Regex comes when you start using all of its special features.
Dan - Matches the word “Dan” in a string. Just writing normal text in a Regex will perform a normal search. And for me versus Regex that's the major breakthrough I've been waiting for. I now understand it so good that I actually could write the last two examples from the top of my mind. Thanks to his talk I began to understand - and actually remember - the fundamentals of Regex. So I'm gonna copy his style of thinking and do the same in this article. He also went through a few bigger examples. In this talk he broke down Regex into its smallest pieces and explained them all, one by one, with examples. On this years JavaZone I attended a talk by Rustam Mehmandarov about Regex.
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