Improved the support of types

src/main/java/org/openrewrite/java/migrate/lang/IfElseIfConstructToSwitch.java

@@ -157,6 +157,13 @@ private boolean validatePotentialCandidate() {
             if (patternMatchers.keySet().stream().anyMatch(instanceOf -> instanceOf.getPattern() == null)) {
                 return false;
             }
+            // Do no harm -> If we do not know how to replace(yet), do not replace
+            if (patternMatchers.keySet().stream().anyMatch(instanceOf -> {
+                J clazz = instanceOf.getClazz();
+                return !(clazz instanceof J.Identifier || clazz instanceof J.FieldAccess || clazz instanceof J.ArrayType || clazz instanceof J.ParameterizedType);
+            })) {
+                return false;
+            }
             boolean nullCaseInSwitch = nullCheckedParameter != null && SemanticallyEqual.areEqual(nullCheckedParameter, switchOn.get());
             boolean hasLastElseBlock = else_ != null;
 
@@ -223,10 +230,9 @@ private Optional<Expression> switchOn() {
         private String getClassName(J.InstanceOf statement) {
             if (statement.getClazz() instanceof J.Identifier) {
                 return ((J.Identifier) statement.getClazz()).getSimpleName();
-            } else if (statement.getClazz() instanceof J.FieldAccess) {
-                return ((J.FieldAccess) statement.getClazz()).toString();
             }
-            throw new IllegalStateException("Found unsupported statement where clazz is " + statement.getClazz());
+
+            return statement.getClazz().toString();
         }
 
         private String getPattern(J.InstanceOf statement) {

src/test/java/org/openrewrite/java/migrate/lang/IfElseIfConstructToSwitchTest.java

@@ -242,6 +242,58 @@ private static class Tester {
         );
     }
 
+    @Test
+    void worksWithGenericsAndArrays() {
+        rewriteRun(
+                //language=java
+                java(
+                """
+                        public class AnotherClass {
+                            public static class SubClass<T> {}
+                        }
+                        """
+                ),
+                //language=java
+                java(
+                        """
+                          class Test {
+                              static String formatter(Object obj) {
+                                  String formatted = "initialValue";
+                                  if (obj == null) {
+                                      formatted = "null";
+                                  } else if (obj instanceof String str)
+                                      formatted = String.format("string %s", str);
+                                  else if (obj instanceof String[] strings) {
+                                      formatted = String.format("strings %s", (Object) strings);
+                                  } else if (obj instanceof Class<?> clazz) {
+                                      formatted = String.format("class %s", clazz.getSimpleName());
+                                  } else if (obj instanceof AnotherClass.SubClass<?> subClazz) {
+                                      formatted = String.format("sub-class %s", subClazz);
+                                  }
+                                  return formatted;
+                              }
+                          }
+                          """,
+                        """
+                          class Test {
+                              static String formatter(Object obj) {
+                                  String formatted = "initialValue";
+                                  switch (obj) {
+                                      case null -> formatted = "null";
+                                      case String str -> formatted = String.format("string %s", str);
+                                      case String[] strings -> formatted = String.format("strings %s", (Object) strings);
+                                      case Class<?> clazz -> formatted = String.format("class %s", clazz.getSimpleName());
+                                      case AnotherClass.SubClass<?> subClazz -> formatted = String.format("sub-class %s", subClazz);
+                                      default -> {}
+                                  }
+                                  return formatted;
+                              }
+                          }
+                          """
+                )
+        );
+    }
+
     @Test
     void defaultSwitchBlockFinalElseStatement() {
         rewriteRun(