Java 7: try with resources

core/src/main/java/hudson/PluginManager.java

@@ -1770,12 +1770,9 @@ public abstract class PluginManager extends AbstractModelObject implements OnMas
 
     protected String identifyPluginShortName(File t) {
         try {
-            JarFile j = new JarFile(t);
-            try {
+            try (JarFile j = new JarFile(t)) {
                 String name = j.getManifest().getMainAttributes().getValue("Short-Name");
-                if (name!=null) return name;
-            } finally {
-                j.close();
+                if (name != null) return name;
             }
         } catch (IOException e) {
             LOGGER.log(WARNING, "Failed to identify the short name from "+t,e);