With non jar files and directories in the lib/ext directory, exceptions are thrown when the file or directory is processed. Should check if the file is a jar file or just suppress the exception message. User should not see these exception messages. Also this is a performance problem because we are processing all the files in the <jre>/lib/ext directory, when we only need to be looking at the jar files. This takes up unnecessary time.

From Java Console:
Checking extension java3d against somedirectory (or non jar file)
java.util.zip.ZipException: Is a directory (msg w/ file: error in opening zip file)
at java.util.zip.ZipFile.open(Native Method)
at java.util.zip.ZipFile.<init>(ZipFile.java:115)
at java.util.jar.JarFile.<init>(JarFile.java:125)
at java.util.jar.JarFile.<init>(JarFile.java:88)
at sun.misc.ExtensionDependency$1.run(ExtensionDependency.java:260)
at java.security.AccessController.doPrivileged(Native Method)
at sun.misc.ExtensionDependency.checkExtensionAgainst(ExtensionDependency.java:253)
at sun.misc.ExtensionDependency.checkExtensionAgainstInstalled(ExtensionDependency.java:214)
at sun.misc.ExtensionDependency.checkExtension(ExtensionDependency.java:180)
at sun.misc.ExtensionDependency.checkExtensions(ExtensionDependency.java:152)
at sun.misc.ExtensionDependency.checkExtensionsDependencies(ExtensionDependency.java:103)
at sun.misc.URLClassPath$JarLoader.parseExtensionsDependencies(URLClassPath.java:732)
at sun.misc.URLClassPath$JarLoader.getClassPath(URLClassPath.java:714)
at sun.misc.URLClassPath.getLoader(URLClassPath.java:227)
at sun.misc.URLClassPath.getResource(URLClassPath.java:137)
at java.net.URLClassLoader$1.run(URLClassLoader.java:193)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:189)
at sun.applet.AppletClassLoader.findClass(AppletClassLoader.java:130)
at sun.plugin.security.PluginClassLoader.findClass(PluginClassLoader.java:185)
at java.lang.ClassLoader.loadClass(ClassLoader.java:308)
at sun.applet.AppletClassLoader.loadClass(AppletClassLoader.java:110)
at java.lang.ClassLoader.loadClass(ClassLoader.java:264)
at sun.applet.AppletClassLoader.loadCode(AppletClassLoader.java:379)
at sun.applet.AppletPanel.createApplet(AppletPanel.java:542)
at sun.plugin.AppletViewer.createApplet(AppletViewer.java:1264)
at sun.applet.AppletPanel.runLoader(AppletPanel.java:478)
at sun.applet.AppletPanel.run(AppletPanel.java:293)
at java.lang.Thread.run(Thread.java:576)