Consider this simple test program:

  public class test {

      public static void main(String[] args) throws Exception {

          String[] s = new String[] { "123" };
          String clName = s.getClass().getName();
          test.class.getClassLoader().loadClass(clName);
      }
  }

This runs fine on JDK 1.5, but throws this exception on JDK 6.0:

Exception in thread "main" java.lang.ClassNotFoundException: [Ljava.lang.String;
        at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:276)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
        at test.main(test.java:7)