Java regex not working - string split

Question

I have a string variable and want to extract a value from it.

String LB0001 = "LB0001"; 
String[] splitString = LB0001.split("LB(.*)");

What I was expecting is that splitString would contain two values, ["LB0001",["0001"]]. However the result is null. Why? I have checked the regex and seems to be correct.

I want to extract "0001". I can do it using other ways, but would like to know what I am doing wrong here.

npinti · Accepted Answer · 2015-12-31 11:36:39Z

2

The split method will split where ever the regular expression provided matches. In your case, the expression LB(.*) matches the provided string completely, thus you get nothing back.

If you want to get the number part, you can split on anything which is not a digit, like so: .split("\\D"). This should get you 1 element which contains 0001.

EDIT: If you want anything after LB you would need to use the Pattern and Matcher class. So basically something like so:

String str = "LB0001";
Pattern p = Pattern.compile("LB(.*?)");
Matcher m = p.matcher(str);
while(m.find())
    System.out.println(m.groups(1));

The above will make use of regular expressions to look for any text which follows LB. I have changed it from .* to .*? in case you have something like so: LB001LB333. The extra ? makes the expression non greedy.

edited Dec 31, 2015 at 11:36

answered Dec 31, 2015 at 11:10

npinti

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2 Comments

Rory Lester Over a year ago

Thank you. I part understand however, i am using myregexp.com to test my regex. When testing on the site, the regex is split into two groups group 1, is the full string match and group 2 is anything after "LB" .Is there a function in java that would give me a similar result?

Rory Lester Over a year ago

Thank you, i ended up doing something similar. Have marked as solution

AbtPst · Accepted Answer · 2015-12-31 15:07:26Z

0

try this

String LB0001 = "LB0001"; 
String[] splitStringAlpha = LB0001.split("[a-zA-Z]+");
System.out.println(splitStringAlpha[0]); 
String[] splitStringNum = LB0001.split("\\D");
System.out.println(splitStringNum[0]);

this should give you

LB
0001

edited Dec 31, 2015 at 15:07

answered Dec 31, 2015 at 11:16

AbtPst

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1 Comment

andolsi zied Over a year ago

\w stands for "word character", usually [A-Za-z0-9_], so LB0001.split("\\W"); return LB0001

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