Update doc for UniqueProperties

[timurt]

https://checkstyle.org/config_misc.html#UniqueProperties

Add example for each existing config to show what code is ok and what code cause violation.
Good example is https://checkstyle.org/config_naming.html#AbstractClassName

please play with module/Check by means of https://checkstyle.org/cmdline.html to understand how it works.

---

PLEASE READ https://github.com/checkstyle/checkstyle/wiki/Good-practice-on-how-to-update-examples

[Divesh2201]

Am working on it.

[Divesh2201]

I have added examples for the Check. Request the admins to verify and point out any changes if required, then I will commit and create PR for the same, after your green signal.

Was Before

Is Now

To configure the check:

$ cat cnf.xml

<!DOCTYPE module PUBLIC
          "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
          "https://checkstyle.org/dtds/configuration_1_3.dtd">

<module name="Checker">
	<module name="UniqueProperties"/>
</module>

$ cat app.properties

key.one=44
key.two=32 
key.one=54

$ java -jar checkstyle-8.40-all.jar -c cnf.xml app.properties

Starting audit...
[ERROR] /home/divesh/Desktop/app.properties:1: Duplicated property 'key.one' (2 occurrence(s)). [UniqueProperties]
Audit done.
Checkstyle ends with 1 errors.

To configure the check to scan custom file extensions:

$ cat cnf.xml

<!DOCTYPE module PUBLIC
          "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
          "https://checkstyle.org/dtds/configuration_1_3.dtd">

<module name="Checker">
	<module name="UniqueProperties">
  		<property name="fileExtensions" value="customproperties"/>
	</module>
</module>

$ cat app.customproperties

key.one=44
key.two=32 
key.one=54 

$ java -jar checkstyle-8.40-all.jar -c cnf.xml app.customproperties

Starting audit...
[ERROR] /home/divesh/Desktop/app.customproperties:1: Duplicated property 'key.one' (2 occurrence(s)). [UniqueProperties]
Audit done.
Checkstyle ends with 1 errors.

$ cat app.properties

key.one=44
key.two=32 
key.one=54 

$ java -jar checkstyle-8.40-all.jar -c cnf.xml app.properties

Starting audit...
Audit done.

To configure the check to scan custom file extensions and properties file:

$ cat cnf.xml

<!DOCTYPE module PUBLIC
          "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
          "https://checkstyle.org/dtds/configuration_1_3.dtd">

<module name="Checker">
	<module name="UniqueProperties">
  		<property name="fileExtensions" value="properties, customproperties"/>
	</module>
</module>

$ cat app.customproperties

key.one=44
key.two=32 
key.one=54 

$ java -jar checkstyle-8.40-all.jar -c cnf.xml app.customproperties

Starting audit...
[ERROR] /home/divesh/Desktop/app.customproperties:1: Duplicated property 'key.one' (2 occurrence(s)). [UniqueProperties]
Audit done.
Checkstyle ends with 1 errors.

$ cat app.properties

key.one=44
key.two=32 
key.one=54 

$ java -jar checkstyle-8.40-all.jar -c cnf.xml app.properties

Starting audit...
[ERROR] /home/divesh/Desktop/app.properties:1: Duplicated property 'key.one' (2 occurrence(s)). [UniqueProperties]
Audit done.
Checkstyle ends with 1 errors.

[romani]

fix is merged