Regex in Java matching specific special characters with number

Question

I would like to have a regex which accepts numeric along with specific special characters (.-,). I just learned about basics of regex and I don't know how come my pattern doesn't work, really need advice.

My Pattern

   ^(([0-9]*)+[.,\-]{0,1})$

(.,-) can only be repeated once, that's {0,1}. Also first should be numeric and last would also be numeric. I really need a little push.

Expected output

122-555-1521 //true

155--122 //false

155,- //false

.-12 //false

123.123. //false

.12 //false

1.2,1-3 //true

can you show us some expected outputs?

Youcef LAIDANI
– Youcef LAIDANI

2018-06-29 09:10:16 +00:00
Commented Jun 29, 2018 at 9:10 — Youcef LAIDANI
– Youcef LAIDANI, Commented Jun 29, 2018 at 9:10
You can use: ^\d+(?:[.,-]\d+)*$

anubhava
– anubhava

2018-06-29 09:15:18 +00:00
Commented Jun 29, 2018 at 9:15 — anubhava
– anubhava, Commented Jun 29, 2018 at 9:15
(OT: {0,1} is shorter, and more commonly, written ?.)

Biffen
– Biffen

2018-06-29 09:15:19 +00:00
Commented Jun 29, 2018 at 9:15 — Biffen
– Biffen, Commented Jun 29, 2018 at 9:15

azro · Accepted Answer · 2018-06-29 09:33:52Z

3

You can use the simple pattern ^(?:\d+[.,-])*\d+$

several digits : \d+
one char from .,- : [.,-]
you can repeat the 2 previous elements : (?:\d[.,-])* ()?: non-capture for performance)
digits at the end : \d+

String[] array = {"122-555-1521", "155--122", "155,-", ".-12", "123.123."};
String pattern = "^(?:\\d+[.,-])*\\d+$";
for(String str : array){
    System.out.println(str+" "+str.matches(pattern));
}

122-555-1521 true
155--122     false
155,-        false
.-12         false
123.123.     false

Working Demo - Regex Demo

edited Jun 29, 2018 at 9:33

answered Jun 29, 2018 at 9:17

azro

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9 Comments

kenjiro jaucian Over a year ago

'thanks for the answer with explanations of the patterns :) I;m very grateful thanks

anubhava Over a year ago

Better to use: ^(?:\d+[.,-])*\d+$

azro Over a year ago

@anubhava better for ? If you don't care about capture or not-capture no need of ?:

anubhava Over a year ago

Better in terms of performance because ^(\d+[\.,-]?)*\d+$ backtracks and takes many times more steps to complete due to ? quantifier. Check this demo and see # of steps taken Using non-capture group and not escaping dot inside character class are just minor improvements.

kenjiro jaucian Over a year ago

can i ask what is the use of that ?: and capture and not-capture? is there a difference

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WolfgangGroiss · Accepted Answer · 2018-06-29 09:22:04Z

1

If I understand correctly, you want to match groups of digits, separated by single non-digit characters from the set of [.,-]?

[0-9]+([.,\-][0-9]+)*

answered Jun 29, 2018 at 9:22

WolfgangGroiss

1992 bronze badges

2 Comments

kenjiro jaucian Over a year ago

sorry i can't use this cause it also accepts spaces

WolfgangGroiss Over a year ago

You're right, I left out the ^ and $. However, azro's answer is more detailed and uses the more compact \d, so better than mine anyway.

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