Question

I have this data

ReferenceDataLocation = as


##############################################################################
#
#   LicenseKey
#       Address Doctor License
#
##############################################################################
LicenseKey = al

which I’d like to capture only key value pairs eg: ReferenceDataLocation = as and LicenseKey = al

I wrote (?xms)(^[\w]+.*?)(?=^[\w]+|\z) regex which is perfect except the fact that it also captures ##### part, which is not key value pair.

Please help me modify the same regex (?xms)(^[\w]+.*?)(?=^[\w]+|\z) to only get ReferenceDataLocation = as and LicenseKey = al

Note: Here you can try out

Update

I tried (?xms)(^[\w]+.*?)(?=^[\w^#]+|\z) it works in the site but gives me an error in java

Exception in thread "main" java.util.regex.PatternSyntaxException: Unclosed character class near index 31
(?xms)(^[\w]+.*?)(?=^[\w^#]+|\Z)
                               ^

Updat Regex that works for me

(?xms)(^[\w]+.*?)(?=^[\w^\s]+|\z)

Answer 1

You can’t do that with a simple regex-match. You can’t account for occurrences like these:

# some words here LicenseKey = al

The regex engine cannot look behind from LicenseKey to the end of the line. This is not supported in Java’s regex engine (unbounded look-behinds).

But what you posted looks like it’s just a properties file. Try this:

import java.io.FileInputStream;
import java.util.Properties;

public class Main {
    public static void main(String[] args) throws Exception {
        Properties properties = new Properties();
        properties.load(new FileInputStream("test.properties"));
        System.out.println(properties.getProperty("ReferenceDataLocation"));
        System.out.println(properties.getProperty("LicenseKey"));
        System.out.println(properties.getProperty("foo"));
    }
}

which will print:

as
al
null

Note that your input file needn’t be called test.properties, you can give it any name you like.

And if you don’t know the keys up front, you can simply iterate over all entries in your properties file like this:

for(Map.Entry<Object, Object> entry : properties.entrySet()) {
  System.out.println(entry.getKey() + " :: " + entry.getValue());
}

which prints:

LicenseKey :: al
ReferenceDataLocation :: as

And there’s also Properties#stringPropertyNames() which returns a Set<String> that represents all keys in the properties file (see the API docs for more info).

See:

• Tutorial: http://download.oracle.com/javase/tutorial/essential/environment/properties.html
• API docs: http://download.oracle.com/javase/7/docs/api/java/util/Properties.html