src/main/java/org/intellimate/izou/sdk/properties/PropertiesAssistant.java
public void registerUpdateListener(Consumer<PropertiesAssistant> listener) {
        if (listener != null)
            listeners.add(new WeakReference<>(listener));
    }
public void registerUpdateListener(Consumer<PropertiesAssistant> listener) {
        if (listener != null)
            listeners.add(new WeakReference<>(listener));
    }
the listener will always be called, when the Properties-file changes.

@param listener the listener