Consistently use class literals for primitive types

To improve consistency and avoid confusion regarding primitive types
and their wrapper types, this commit ensures that we always use class
literals for primitive types.

For example, instead of using the `Void.TYPE` constant, we now
consistently use `void.class`.

integration-tests/src/test/java/org/springframework/expression/spel/support/BeanFactoryTypeConverter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -94,7 +94,7 @@ public boolean canConvert(TypeDescriptor sourceTypeDescriptor, TypeDescriptor ta
 
 	@Override
 	public Object convertValue(Object value, TypeDescriptor sourceType, TypeDescriptor targetType) {
-		if (targetType.getType() == Void.class || targetType.getType() == Void.TYPE) {
+		if (targetType.getType() == Void.class || targetType.getType() == void.class) {
 			return null;
 		}
 		if (conversionService.canConvert(sourceType, targetType)) {

spring-aop/src/main/java/org/springframework/aop/framework/CglibAopProxy.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -417,7 +417,7 @@ private static Object processReturnType(
 			returnValue = proxy;
 		}
 		Class<?> returnType = method.getReturnType();
-		if (returnValue == null && returnType != Void.TYPE && returnType.isPrimitive()) {
+		if (returnValue == null && returnType != void.class && returnType.isPrimitive()) {
 			throw new AopInvocationException(
 					"Null return value from advice does not match primitive return type for: " + method);
 		}

spring-aop/src/main/java/org/springframework/aop/framework/JdkDynamicAopProxy.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -230,7 +230,7 @@ else if (!this.advised.opaque && method.getDeclaringClass().isInterface() &&
 				// a reference to itself in another returned object.
 				retVal = proxy;
 			}
-			else if (retVal == null && returnType != Void.TYPE && returnType.isPrimitive()) {
+			else if (retVal == null && returnType != void.class && returnType.isPrimitive()) {
 				throw new AopInvocationException(
 						"Null return value from advice does not match primitive return type for: " + method);
 			}

spring-aop/src/main/java/org/springframework/aop/support/Pointcuts.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -101,7 +101,7 @@ private static class SetterPointcut extends StaticMethodMatcherPointcut implemen
 		public boolean matches(Method method, Class<?> targetClass) {
 			return (method.getName().startsWith("set") &&
 					method.getParameterCount() == 1 &&
-					method.getReturnType() == Void.TYPE);
+					method.getReturnType() == void.class);
 		}
 
 		private Object readResolve() {
@@ -127,7 +127,7 @@ private static class GetterPointcut extends StaticMethodMatcherPointcut implemen
 		public boolean matches(Method method, Class<?> targetClass) {
 			return (method.getName().startsWith("get") &&
 					method.getParameterCount() == 0 &&
-					method.getReturnType() != Void.TYPE);
+					method.getReturnType() != void.class);
 		}
 
 		private Object readResolve() {

spring-beans/src/main/java/org/springframework/beans/PropertyDescriptorUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -68,7 +68,7 @@ public static Collection<? extends PropertyDescriptor> determineBasicProperties(
 				setter = true;
 				nameIndex = 3;
 			}
-			else if (methodName.startsWith("get") && method.getParameterCount() == 0 && method.getReturnType() != Void.TYPE) {
+			else if (methodName.startsWith("get") && method.getParameterCount() == 0 && method.getReturnType() != void.class) {
 				setter = false;
 				nameIndex = 3;
 			}
@@ -152,7 +152,7 @@ public static Class<?> findPropertyType(@Nullable Method readMethod, @Nullable M
 				throw new IntrospectionException("Bad read method arg count: " + readMethod);
 			}
 			propertyType = readMethod.getReturnType();
-			if (propertyType == Void.TYPE) {
+			if (propertyType == void.class) {
 				throw new IntrospectionException("Read method returns void: " + readMethod);
 			}
 		}
@@ -197,11 +197,11 @@ public static Class<?> findIndexedPropertyType(String name, @Nullable Class<?> p
 			if (params.length != 1) {
 				throw new IntrospectionException("Bad indexed read method arg count: " + indexedReadMethod);
 			}
-			if (params[0] != Integer.TYPE) {
+			if (params[0] != int.class) {
 				throw new IntrospectionException("Non int index to indexed read method: " + indexedReadMethod);
 			}
 			indexedPropertyType = indexedReadMethod.getReturnType();
-			if (indexedPropertyType == Void.TYPE) {
+			if (indexedPropertyType == void.class) {
 				throw new IntrospectionException("Indexed read method returns void: " + indexedReadMethod);
 			}
 		}
@@ -211,7 +211,7 @@ public static Class<?> findIndexedPropertyType(String name, @Nullable Class<?> p
 			if (params.length != 2) {
 				throw new IntrospectionException("Bad indexed write method arg count: " + indexedWriteMethod);
 			}
-			if (params[0] != Integer.TYPE) {
+			if (params[0] != int.class) {
 				throw new IntrospectionException("Non int index to indexed write method: " + indexedWriteMethod);
 			}
 			if (indexedPropertyType != null) {

spring-context/src/test/java/org/springframework/aop/framework/ProxyFactoryBeanTests.java

@@ -698,7 +698,7 @@ public PointcutForVoid() {
 			setPointcut(new DynamicMethodMatcherPointcut() {
 				@Override
 				public boolean matches(Method m, @Nullable Class<?> targetClass, Object... args) {
-					return m.getReturnType() == Void.TYPE;
+					return m.getReturnType() == void.class;
 				}
 			});
 		}

spring-core/src/main/java/org/springframework/aot/hint/BindingReflectionHintsRegistrar.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -107,7 +107,7 @@ private void registerReflectionHints(ReflectionHints hints, Set<Type> seen, Type
 						if (methodName.startsWith("set") && method.getParameterCount() == 1) {
 							registerPropertyHints(hints, seen, method, 0);
 						}
-						else if ((methodName.startsWith("get") && method.getParameterCount() == 0 && method.getReturnType() != Void.TYPE) ||
+						else if ((methodName.startsWith("get") && method.getParameterCount() == 0 && method.getReturnType() != void.class) ||
 								(methodName.startsWith("is") && method.getParameterCount() == 0 && method.getReturnType() == boolean.class)) {
 							registerPropertyHints(hints, seen, method, -1);
 						}

spring-core/src/main/java/org/springframework/core/annotation/AnnotatedMethod.java

@@ -137,7 +137,7 @@ public MethodParameter getReturnValueType(@Nullable Object returnValue) {
 	 * Return {@code true} if the method's return type is void, {@code false} otherwise.
 	 */
 	public boolean isVoid() {
-		return Void.TYPE.equals(getReturnType().getParameterType());
+		return (getReturnType().getParameterType() == void.class);
 	}
 
 	/**

spring-core/src/test/java/org/springframework/core/MethodParameterTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -52,7 +52,7 @@ class MethodParameterTests {
 
 	@BeforeEach
 	void setup() throws NoSuchMethodException {
-		method = getClass().getMethod("method", String.class, Long.TYPE);
+		method = getClass().getMethod("method", String.class, long.class);
 		stringParameter = new MethodParameter(method, 0);
 		longParameter = new MethodParameter(method, 1);
 		intReturnType = new MethodParameter(method, -1);
@@ -72,7 +72,7 @@ void equals() throws NoSuchMethodException {
 		assertThat(intReturnType).isNotEqualTo(stringParameter);
 		assertThat(intReturnType).isNotEqualTo(longParameter);
 
-		Method method = getClass().getMethod("method", String.class, Long.TYPE);
+		Method method = getClass().getMethod("method", String.class, long.class);
 		MethodParameter methodParameter = new MethodParameter(method, 0);
 		assertThat(methodParameter).isEqualTo(stringParameter);
 		assertThat(stringParameter).isEqualTo(methodParameter);
@@ -86,7 +86,7 @@ void testHashCode() throws NoSuchMethodException {
 		assertThat(longParameter.hashCode()).isEqualTo(longParameter.hashCode());
 		assertThat(intReturnType.hashCode()).isEqualTo(intReturnType.hashCode());
 
-		Method method = getClass().getMethod("method", String.class, Long.TYPE);
+		Method method = getClass().getMethod("method", String.class, long.class);
 		MethodParameter methodParameter = new MethodParameter(method, 0);
 		assertThat(methodParameter.hashCode()).isEqualTo(stringParameter.hashCode());
 		assertThat(methodParameter.hashCode()).isNotEqualTo(longParameter.hashCode());

spring-core/src/test/java/org/springframework/core/annotation/SynthesizingMethodParameterTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -43,7 +43,7 @@ class SynthesizingMethodParameterTests {
 
 	@BeforeEach
 	void setUp() throws NoSuchMethodException {
-		method = getClass().getMethod("method", String.class, Long.TYPE);
+		method = getClass().getMethod("method", String.class, long.class);
 		stringParameter = new SynthesizingMethodParameter(method, 0);
 		longParameter = new SynthesizingMethodParameter(method, 1);
 		intReturnType = new SynthesizingMethodParameter(method, -1);
@@ -63,7 +63,7 @@ void equals() throws NoSuchMethodException {
 		assertThat(intReturnType).isNotEqualTo(stringParameter);
 		assertThat(intReturnType).isNotEqualTo(longParameter);
 
-		Method method = getClass().getMethod("method", String.class, Long.TYPE);
+		Method method = getClass().getMethod("method", String.class, long.class);
 		MethodParameter methodParameter = new SynthesizingMethodParameter(method, 0);
 		assertThat(methodParameter).isEqualTo(stringParameter);
 		assertThat(stringParameter).isEqualTo(methodParameter);
@@ -83,7 +83,7 @@ void testHashCode() throws NoSuchMethodException {
 		assertThat(longParameter.hashCode()).isEqualTo(longParameter.hashCode());
 		assertThat(intReturnType.hashCode()).isEqualTo(intReturnType.hashCode());
 
-		Method method = getClass().getMethod("method", String.class, Long.TYPE);
+		Method method = getClass().getMethod("method", String.class, long.class);
 		SynthesizingMethodParameter methodParameter = new SynthesizingMethodParameter(method, 0);
 		assertThat(methodParameter.hashCode()).isEqualTo(stringParameter.hashCode());
 		assertThat(methodParameter.hashCode()).isNotEqualTo(longParameter.hashCode());

spring-core/src/test/java/org/springframework/core/convert/TypeDescriptorTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -303,7 +303,7 @@ void fieldListOfListUnknown() throws Exception {
 	void fieldArray() throws Exception {
 		TypeDescriptor typeDescriptor = new TypeDescriptor(TypeDescriptorTests.class.getDeclaredField("intArray"));
 		assertThat(typeDescriptor.isArray()).isTrue();
-		assertThat(typeDescriptor.getElementTypeDescriptor().getType()).isEqualTo(Integer.TYPE);
+		assertThat(typeDescriptor.getElementTypeDescriptor().getType()).isEqualTo(int.class);
 		assertThat(typeDescriptor.toString()).isEqualTo("int[]");
 	}
 
@@ -359,7 +359,7 @@ void valueOfPrimitive() {
 		assertThat(typeDescriptor.isArray()).isFalse();
 		assertThat(typeDescriptor.isCollection()).isFalse();
 		assertThat(typeDescriptor.isMap()).isFalse();
-		assertThat(typeDescriptor.getType()).isEqualTo(Integer.TYPE);
+		assertThat(typeDescriptor.getType()).isEqualTo(int.class);
 		assertThat(typeDescriptor.getObjectType()).isEqualTo(Integer.class);
 	}
 
@@ -369,7 +369,7 @@ void valueOfArray() {
 		assertThat(typeDescriptor.isArray()).isTrue();
 		assertThat(typeDescriptor.isCollection()).isFalse();
 		assertThat(typeDescriptor.isMap()).isFalse();
-		assertThat(typeDescriptor.getElementTypeDescriptor().getType()).isEqualTo(Integer.TYPE);
+		assertThat(typeDescriptor.getElementTypeDescriptor().getType()).isEqualTo(int.class);
 	}
 
 	@Test

spring-expression/src/main/java/org/springframework/expression/spel/CodeFlow.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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.
@@ -454,31 +454,31 @@ public static String toJvmDescriptor(Class<?> clazz) {
 			}
 		}
 		if (clazz.isPrimitive()) {
-			if (clazz == Boolean.TYPE) {
+			if (clazz == boolean.class) {
 				sb.append('Z');
 			}
-			else if (clazz == Byte.TYPE) {
+			else if (clazz == byte.class) {
 				sb.append('B');
 			}
-			else if (clazz == Character.TYPE) {
+			else if (clazz == char.class) {
 				sb.append('C');
 			}
-			else if (clazz == Double.TYPE) {
+			else if (clazz == double.class) {
 				sb.append('D');
 			}
-			else if (clazz == Float.TYPE) {
+			else if (clazz == float.class) {
 				sb.append('F');
 			}
-			else if (clazz == Integer.TYPE) {
+			else if (clazz == int.class) {
 				sb.append('I');
 			}
-			else if (clazz == Long.TYPE) {
+			else if (clazz == long.class) {
 				sb.append('J');
 			}
-			else if (clazz == Short.TYPE) {
+			else if (clazz == short.class) {
 				sb.append('S');
 			}
-			else if (clazz == Void.TYPE) {
+			else if (clazz == void.class) {
 				sb.append('V');
 			}
 		}

spring-expression/src/main/java/org/springframework/expression/spel/ast/Indexer.java

@@ -385,49 +385,49 @@ else if (arrayComponentType == short.class) {
 
 	private Object accessArrayElement(Object ctx, int idx) throws SpelEvaluationException {
 		Class<?> arrayComponentType = ctx.getClass().componentType();
-		if (arrayComponentType == Boolean.TYPE) {
+		if (arrayComponentType == boolean.class) {
 			boolean[] array = (boolean[]) ctx;
 			checkAccess(array.length, idx);
 			this.exitTypeDescriptor = "Z";
 			return array[idx];
 		}
-		else if (arrayComponentType == Byte.TYPE) {
+		else if (arrayComponentType == byte.class) {
 			byte[] array = (byte[]) ctx;
 			checkAccess(array.length, idx);
 			this.exitTypeDescriptor = "B";
 			return array[idx];
 		}
-		else if (arrayComponentType == Character.TYPE) {
+		else if (arrayComponentType == char.class) {
 			char[] array = (char[]) ctx;
 			checkAccess(array.length, idx);
 			this.exitTypeDescriptor = "C";
 			return array[idx];
 		}
-		else if (arrayComponentType == Double.TYPE) {
+		else if (arrayComponentType == double.class) {
 			double[] array = (double[]) ctx;
 			checkAccess(array.length, idx);
 			this.exitTypeDescriptor = "D";
 			return array[idx];
 		}
-		else if (arrayComponentType == Float.TYPE) {
+		else if (arrayComponentType == float.class) {
 			float[] array = (float[]) ctx;
 			checkAccess(array.length, idx);
 			this.exitTypeDescriptor = "F";
 			return array[idx];
 		}
-		else if (arrayComponentType == Integer.TYPE) {
+		else if (arrayComponentType == int.class) {
 			int[] array = (int[]) ctx;
 			checkAccess(array.length, idx);
 			this.exitTypeDescriptor = "I";
 			return array[idx];
 		}
-		else if (arrayComponentType == Long.TYPE) {
+		else if (arrayComponentType == long.class) {
 			long[] array = (long[]) ctx;
 			checkAccess(array.length, idx);
 			this.exitTypeDescriptor = "J";
 			return array[idx];
 		}
-		else if (arrayComponentType == Short.TYPE) {
+		else if (arrayComponentType == short.class) {
 			short[] array = (short[]) ctx;
 			checkAccess(array.length, idx);
 			this.exitTypeDescriptor = "S";