Use pattern matching for instanceof

Converts instanceof checks to use Java 17 pattern matching where
applicable, eliminating explicit casting and reducing boilerplate.
This makes the code more concise and type-safe.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: oschwald

src/main/java/com/maxmind/db/Decoder.java

@@ -158,8 +158,7 @@ private <T> Object decodeByType(
                 return this.decodeMap(size, cls, genericType);
             case ARRAY:
                 Class<?> elementClass = Object.class;
-                if (genericType instanceof ParameterizedType) {
-                    ParameterizedType ptype = (ParameterizedType) genericType;
+                if (genericType instanceof ParameterizedType ptype) {
                     java.lang.reflect.Type[] actualTypes = ptype.getActualTypeArguments();
                     if (actualTypes.length == 1) {
                         elementClass = (Class<?>) actualTypes[0];
@@ -319,8 +318,7 @@ private <T> Object decodeMap(
     ) throws IOException {
         if (Map.class.isAssignableFrom(cls) || cls.equals(Object.class)) {
             Class<?> valueClass = Object.class;
-            if (genericType instanceof ParameterizedType) {
-                ParameterizedType ptype = (ParameterizedType) genericType;
+            if (genericType instanceof ParameterizedType ptype) {
                 java.lang.reflect.Type[] actualTypes = ptype.getActualTypeArguments();
                 if (actualTypes.length == 2) {
                     Class<?> keyClass = (Class<?>) actualTypes[0];

src/test/java/com/maxmind/db/DecoderTest.java

@@ -465,8 +465,8 @@ private static <T> void testTypeDecoding(Type type, Map<T, byte[]> tests)
                         String key = (String) keyObject;
                         Object value = expectMap.get(key);
 
-                        if (value instanceof Object[]) {
-                            assertArrayEquals((Object[]) value, (Object[]) got.get(key), desc);
+                        if (value instanceof Object[] arrayValue) {
+                            assertArrayEquals(arrayValue, (Object[]) got.get(key), desc);
                         } else {
                             assertEquals(value, got.get(key), desc);
                         }