Java regex returns only single match

Question

I have file with content:

~LayerData
type="waypointlist"
type="waypointlistend"
type="track" name="Track1" color=#695cbb
type="trackpoint" latitude="43.5032064" longitude="16.4266248"
type="trackpoint" latitude="43.5071074767561" longitude="16.48329290000057"
type="trackend"
~EndLayerData
~LayerData
type="waypointlist"
type="waypointlistend"
type="track" name="Track2" color=#000000
type="trackpoint" latitude="43.51037193515589" longitude="16.491883500895977"
type="trackpoint" latitude="43.521582832754135" longitude="16.473187288140295"
type="trackend"
~EndLayerData

I'm extracing LayerData -> EndLayerData matches using:

Pattern p = Pattern.compile("(~LayerData(.|\n)*~EndLayerData)");
Matcher m = p.matcher(s);

As a result I get m.group() with three items: first two are identical and contain the complete file. Last one is "\n". I expected to receive Track1 and Track2 separated.

Remember to escape properly. a single ` in a string becomes \`. \n is a line break, if you want to match it you need to use \\n. — Polygnome
– Polygnome, Commented Jul 28, 2020 at 7:05
@TimBiegeleisen: I'm trying to extract two LayerData sections — ernest
– ernest, Commented Jul 28, 2020 at 7:31
@Polygnome: This is copy-paste from IDE, there is \\ in source code — ernest
– ernest, Commented Jul 28, 2020 at 7:31

The fourth bird · Accepted Answer · 2020-07-28 09:37:07Z

You could match LayerData followed by all lines that do not start with either LayerData or EndLayerData using a negative lookahead.

^~LayerData(?:\R(?!~(?:End)?LayerData).*)*\R~EndLayerData

Explanation

^~LayerData Match LayerData from the start of the string
(?: Non capture group
- \R(?!~(?:End)?LayerData) Match a newline, assert what is directly to the right is not EndLayerData or LayerData
- .* Match the rest of the line
)* Close the group and repeat 0+ times to get all lines
\R~EndLayerData Match a newline and EndLayerData

In Java with double escaped backslashes:

String regex = "^~LayerData(?:\\R(?!~(?:End)?LayerData).*)*\\R~EndLayerData";

Regex demo | Java demo

Example code

String regex = "^~LayerData(?:\\R(?!~(?:End)?LayerData).*)*\\R~EndLayerData";
String string = "...";

Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE);
Matcher matcher = pattern.matcher(string);

while (matcher.find()) {
    System.out.println(matcher.group(0));
}

sturman · Accepted Answer · 2020-07-28 06:27:17Z

0

Try this pattern

(~LayerData(.|\n)*?~EndLayerData)

answered Jul 28, 2020 at 6:27

sturman

5831 gold badge4 silver badges19 bronze badges

1 Comment

ernest Over a year ago

Thanks, but same result. The problem is that EndLayerData LayerData in the middle of file is not detected, not the LayerData content itself.

Rishi · Accepted Answer · 2020-07-28 07:46:02Z

0

Update: Use Code Generator under tools in regex101 to get language-specific regex.

String regex = "\\~LayerData(.|\\n)*?\\~EndLayerData";
Pattern pattern = Pattern.compile(regex); 
Matcher matcher = pattern.matcher(string); 
while (matcher.find()) { 
System.out.println(matcher.group(0)); 
}

Earlier Answer: You are not getting the match properly as the regex you are using is not proper. Since it matches with everything that starts with "~LayerData" and ends with "~EndLayerData", the whole file is getting matched. Creating an appropriate regex using regex101.com (helps in visualizing) and using that should fix the issue.

edited Jul 28, 2020 at 7:46

answered Jul 28, 2020 at 6:58

Rishi

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3 Comments

ernest Over a year ago

This is the regex: regex101.com/r/JG3W09/1, but the problem here is setting the /g flag, which is enabled by default in Java, but the result is different, the on regex101.com

ernest Over a year ago

Not works, please take a look at online Java test: tpcg.io/cxW9uGRz

Rishi Over a year ago

@ernest Works fine. Please take a look: tpcg.io/W3B7f1kd

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