Updated JdkVersion regarding Java 9 support

- JdkVersion#JAVA_19 is now properly set to 6 instead of 5.
 - Javadoc for getMajorJavaVersion() now references currently supported
   Java versions.

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

@@ -17,15 +17,16 @@
 package org.springframework.core;
 
 /**
- * Internal helper class used to find the Java/JVM version
- * that Spring is operating on, to allow for automatically
- * adapting to the present platform's capabilities.
+ * Internal helper class used to find the Java/JVM version that Spring is
+ * operating on, to allow for automatically adapting to the present platform's
+ * capabilities.
  *
  * <p>Note that Spring requires JVM 1.6 or higher, as of Spring 4.0.
  *
  * @author Rod Johnson
  * @author Juergen Hoeller
  * @author Rick Evans
+ * @author Sam Brannen
  */
 public abstract class JdkVersion {
 
@@ -62,7 +63,7 @@ public abstract class JdkVersion {
 	/**
 	 * Constant identifying the 1.9 JVM (Java 9).
 	 */
-	public static final int JAVA_19 = 5;
+	public static final int JAVA_19 = 6;
 
 
 	private static final String javaVersion;
@@ -101,12 +102,11 @@ public abstract class JdkVersion {
 	/**
 	 * Get the major version code. This means we can do things like
 	 * {@code if (getMajorJavaVersion() >= JAVA_17)}.
-	 * @return a code comparable to the JAVA_XX codes in this class
-	 * @see #JAVA_13
-	 * @see #JAVA_14
-	 * @see #JAVA_15
+	 * @return a code comparable to the {@code JAVA_XX} codes in this class
 	 * @see #JAVA_16
-	 * @see #JAVA_17
+     * @see #JAVA_17
+     * @see #JAVA_18
+     * @see #JAVA_19
 	 */
 	public static int getMajorJavaVersion() {
 		return majorJavaVersion;