The resourcebundle.inspector project can inspect projects of unused properties keys or duplicate keys.
'de.alpharogroup:resourcebundle.inspector.core:2.0.0'
<dependency>
<groupId>de.alpharogroup</groupId>
<artifactId>resourcebundle.inspector.core</artifactId>
<version>2.0.0</version>
</dependency>
<dependency org="de.alpharogroup" name="resourcebundle.inspector.core" rev="2.0.0"/>
"de.alpharogroup", "resourcebundle.inspector.core", "2.0.0"