[Patch][JDK10] Use Class.getPackageName() where possible

[Christoph Dreis]

Hey,

I noticed two places in the codebase that could call JDK 9's new method
Class.getPackageName().

Would be happy if this is sponsored in case the patch is correct.

Cheers,
Christoph

====== PATCH =======
diff -r 438e0c9f2f17
src/java.base/share/classes/java/io/ObjectStreamClass.java
--- a/src/java.base/share/classes/java/io/ObjectStreamClass.java	Mon
Oct 30 17:49:33 2017 -0700
+++ b/src/java.base/share/classes/java/io/ObjectStreamClass.java	Fri
Nov 03 01:47:04 2017 +0100
@@ -1587,11 +1587,7 @@
      * Returns package name of given class.
      */
     private static String getPackageName(Class<?> cl) {
-        String s = cl.getName();
-        int i = s.lastIndexOf('[');
-        i = (i < 0) ? 0 : i + 2;
-        int j = s.lastIndexOf('.');
-        return (i < j) ? s.substring(i, j) : "";
+        return cl.getPackageName();
     }
 
     /**
diff -r 438e0c9f2f17
src/java.base/share/classes/java/lang/reflect/Proxy.java
--- a/src/java.base/share/classes/java/lang/reflect/Proxy.java	Mon Oct 30
17:49:33 2017 -0700
+++ b/src/java.base/share/classes/java/lang/reflect/Proxy.java	Fri Nov 03
01:47:04 2017 +0100
@@ -1034,11 +1034,8 @@
 
                 // do permission check if the caller is in a different
runtime package
                 // of the proxy class
-                int n = proxyClass.getName().lastIndexOf('.');
-                String pkg = (n == -1) ? "" :
proxyClass.getName().substring(0, n);
-
-                n = caller.getName().lastIndexOf('.');
-                String callerPkg = (n == -1) ? "" :
caller.getName().substring(0, n);
+                String pkg = proxyClass.getPackageName();
+                String callerPkg = caller.getPackageName();
 
                 if (pcl != ccl || !pkg.equals(callerPkg)) {
                     sm.checkPermission(new
ReflectPermission("newProxyInPackage." + pkg));