Apply pattern matching for instanceof across codebase (#435)

* Initial plan

* Apply pattern matching for instanceof (Java 17 feature)

Co-authored-by: ChristianHoesel <[email protected]>

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: ChristianHoesel <[email protected]>

Author: Copilot

src/main/java/com/bitctrl/resource/Configuration.java

@@ -274,8 +274,8 @@ public Set<String> stringPropertyNames() {
 
 		final Set<String> keys = new HashSet<>();
 		for (final Object key : configuration.keySet()) {
-			if (key instanceof String) {
-				keys.add((String) key);
+			if (key instanceof final String stringKey) {
+				keys.add(stringKey);
 			}
 		}
 		return keys;

src/main/java/com/bitctrl/rmi/RemoteTools.java

@@ -87,7 +87,7 @@ public static void init(final StoppableApplication application, final String[] a
 				} catch (final NotBoundException ex) {
 					throw new IllegalStateException(ex);
 				} catch (final UnmarshalException ex) {
-					if (ex.getCause() instanceof SocketException) {
+					if (ex.getCause() instanceof final SocketException socketEx) {
 						// Verbindungsabruch, weil Applikation beendet wurde
 						System.exit(0);
 					} else {

src/main/java/com/bitctrl/util/TreeProperties.java

@@ -528,8 +528,8 @@ public Set<String> stringPropertyNames() {
 
 		final Set<String> keys = new HashSet<>();
 		for (final Object key : keySet()) {
-			if (key instanceof String) {
-				keys.add((String) key);
+			if (key instanceof final String stringKey) {
+				keys.add(stringKey);
 			}
 		}
 		return keys;

src/main/java/com/bitctrl/util/monitor/SubMonitor.java

@@ -504,9 +504,9 @@ public static SubMonitor convert(IMonitor monitor, final String taskName, final
 
 		// Optimization: if the given monitor already a SubMonitor, no
 		// conversion is necessary
-		if (monitor instanceof SubMonitor) {
-			monitor.beginTask(taskName, work);
-			return (SubMonitor) monitor;
+		if (monitor instanceof final SubMonitor subMonitor) {
+			subMonitor.beginTask(taskName, work);
+			return subMonitor;
 		}
 
 		monitor.beginTask(taskName, MINIMUM_RESOLUTION);