ExternalResourceHolder (checkstyle 10.1 API)

All Known Implementing Classes:

AbstractHeaderCheck, HeaderCheck, ImportControlCheck, RegexpHeaderCheck, SuppressionFilter, SuppressionXpathFilter, TreeWalker

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
```
@FunctionalInterface
public interface ExternalResourceHolder
```
The following interface should be implemented by each module (inheritor of AbstractCheck, implementor of FileSetCheck, or Filter) which uses external resources of any kind for its configuration. Such modules must declare external resource locations as a set of String which will be returned from getExternalResourceLocations(). This allows Checkstyle to invalidate (clear) cache when the content of at least one external configuration resource of the module is changed.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`java.util.Set<java.lang.String>`	`getExternalResourceLocations()`	Returns a set of external configuration resource locations which are used by the module.

- Method Detail
  - getExternalResourceLocations
```
java.util.Set<java.lang.String> getExternalResourceLocations()
```
    Returns a set of external configuration resource locations which are used by the module. ATTENTION! If 'getExternalResourceLocations()' return null, there will be NullPointerException in Checker. Such behaviour will signal that your module (check or filter) is designed incorrectly. It make sense to return an empty set from 'getExternalResourceLocations()' only for composite modules like TreeWalker.
    
    Returns:
    
    a set of external configuration resource locations which are used by the module.