Fix typo in ClassUtils.forName()

See gh-31258
Closes gh-31428

spring-core/src/main/java/org/springframework/util/ClassUtils.java

@@ -306,7 +306,7 @@ public abstract class ClassUtils {
 		catch (ClassNotFoundException ex) {
 			int lastDotIndex = name.lastIndexOf(PACKAGE_SEPARATOR);
 			int previousDotIndex = name.lastIndexOf(PACKAGE_SEPARATOR, lastDotIndex -1);
-			if (lastDotIndex != -1 && previousDotIndex != 1 && Character.isUpperCase(name.charAt(previousDotIndex + 1))) {
+			if (lastDotIndex != -1 && previousDotIndex != -1 && Character.isUpperCase(name.charAt(previousDotIndex + 1))) {
 				String nestedClassName =
 						name.substring(0, lastDotIndex) + NESTED_CLASS_SEPARATOR + name.substring(lastDotIndex + 1);
 				try {

spring-core/src/test/java/a/ClassHavingNestedClass.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2002-2023 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package a;
+
+/**
+ * Test class for {@code org.springframework.util.ClassUtilsTests}.
+ *
+ * @author Johnny Lim
+ */
+public class ClassHavingNestedClass {
+
+	public static class NestedClass {
+	}
+
+}

spring-core/src/test/java/org/springframework/util/ClassUtilsTests.java

@@ -86,6 +86,8 @@ class ClassUtilsTests {
 	void forNameWithNestedType() throws ClassNotFoundException {
 		assertThat(ClassUtils.forName("org.springframework.util.ClassUtilsTests$NestedClass", classLoader)).isEqualTo(NestedClass.class);
 		assertThat(ClassUtils.forName("org.springframework.util.ClassUtilsTests.NestedClass", classLoader)).isEqualTo(NestedClass.class);
+		assertThat(ClassUtils.forName("a.ClassHavingNestedClass$NestedClass", classLoader)).isEqualTo(a.ClassHavingNestedClass.NestedClass.class);
+		assertThat(ClassUtils.forName("a.ClassHavingNestedClass.NestedClass", classLoader)).isEqualTo(a.ClassHavingNestedClass.NestedClass.class);
 	}
 
 	@Test