Deprecate JdkVersion (for optimistic compatibility with newer JDK generations)

Issue: SPR-13312

spring-core/src/main/java/org/springframework/core/DefaultParameterNameDiscoverer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2015 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.
@@ -16,6 +16,8 @@
 
 package org.springframework.core;
 
+import org.springframework.util.ClassUtils;
+
 /**
  * Default implementation of the {@link ParameterNameDiscoverer} strategy interface,
  * using the Java 8 standard reflection mechanism (if available), and falling back
@@ -31,8 +33,8 @@ package org.springframework.core;
  */
 public class DefaultParameterNameDiscoverer extends PrioritizedParameterNameDiscoverer {
 
-	private static final boolean standardReflectionAvailable =
-			(JdkVersion.getMajorJavaVersion() >= JdkVersion.JAVA_18);
+	private static final boolean standardReflectionAvailable = ClassUtils.isPresent(
+			"java.lang.reflect.Executable", DefaultParameterNameDiscoverer.class.getClassLoader());
 
 
 	public DefaultParameterNameDiscoverer() {

spring-core/src/main/java/org/springframework/core/JdkVersion.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2015 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.
@@ -27,7 +27,10 @@ package org.springframework.core;
  * @author Juergen Hoeller
  * @author Rick Evans
  * @author Sam Brannen
+ * @deprecated as of Spring 4.2.1, in favor of direct checks for the desired
+ * JDK API variants via reflection
  */
+@Deprecated
 public abstract class JdkVersion {
 
 	/**