使用正则表达式验证冒号分隔的输入

Question

I'm reading in a file for a Java application which has data separated by colons in the format:

test : test : 0 : 0

Where the first two segments are names of something and the last two are digits.

The match should fail if the input is not formatted in that exact way above (aside from the data being different)

test : test : 0 : 0 -----> pass
: test: 0 : 0       -----> fail
0 : test : 0 : test -----> fail
test test : 0 : 0   -----> fail

So the match will fail if there are any segments omitted, if the digits and words do not appear where they should, ie word : word : digit : digit , and there has to be 3 colons and 4 segments no more no less as above.

This is where I have gotten so far but it's not quite right:

^\D+(?:\s\:\s\w+)*$

Answer 1

You may use a regex like

^[a-zA-Z]+\s*:\s*[a-zA-Z]+(?:\s*:\s*\d+){2}$

Details

• ^ - start of string (implicit in String#matches )
• [a-zA-Z]+ - 1+ ASCII letters
• \\s*:\\s* - a : enclosed with 0+ whitespaces
• [a-zA-Z]+ - 1+ ASCII letters
• (?:\\s*:\\s*\\d+){2} - two occurrences of : enclosed with 0+ whitespaces and then 1+ digits
• $ - end of string (implicit in String#matches )

NOTE : If there must be an obligatory single space between the items, you need to replace \\s* with \\s . To match 1 or more whitespaces, \\s* must be turned into \\s+ .

In Java, you may write it as

s.matches("[a-zA-Z]+\\s*:\\s*[a-zA-Z]+(?:\\s*:\\s*\\d+){2}")

See the regex demo

Answer 2

I would just use String#matches on each line, with the following pattern:

[a-z]+ : [a-z]+ : [0-9]+ : [0-9]+

For example:

String line = "test : test : 0 : 0";
if (line.matches("[a-z]+ : [a-z]+ : [0-9]+ : [0-9]+")) {
    System.out.println("Found a match");
}

Answer 3

Here you go (demo at Regex101 ):

[a-zA-Z]+\s+:\s+[a-zA-Z]+\s+:\s+\d+\s+:\s+\d+

Explanation:

• [a-zA-Z]+ stands for 1 or more letters ( + is the modifiers allowing to match the previous statement at least once
• \\s+ stands for 1 or more
• : is the : character, literally
• \\d+ stands for at least one digit (remove the + to match one digit exactly)

Finally, compose those parts according to your needs. You might want to make the Regex make stricter replacing the \\s+ with only one empty space .

Validate the String using the method String::matches (don't forget to use two slashes \\\\ ):

boolean isValid = string.matches("[a-zA-Z]+\\s+:\\s+[a-zA-Z]+\\s+:\\s+\\d+\\s+:\\s+\\d+");