Class.forName returning null

Question

I've seen a post regarding whether or not Class.forName can return null here and everyone seems to think it can't (or wont). However, it is returning null for me with this code:

  public void init() {
    File binDriectory = new File("./bin/dft");
    String[] files = binDriectory.list();
    for (String file : files) {
      if (file.endsWith(".class")) {
        if (file.indexOf("DataReader") > 0) {
          //strip off the ".class"
          String className = file.substring(0, file.indexOf(".class"));

          try {
            //load the class
            Class readerclass = Class.forName("dft." + className);
            //get the file extension of the file type this class deals with

            /* NullPointerException thrown here in call to getMthod() */

            Method getExtensionMethod = readerClass.getMethod("getFileExtension", null);
            String extension = (String) getExtensionMethod.invoke(readerClass.newInstance(), null);
            //add the extension and class to the class map
            classMap.put(extension, readerClass);
            //add the extension to the list of reader file extensions
            readerExtensions.add(extension);
          }
          catch (ClassNotFoundException e) {
            System.err.println("**WARNING: class not found: dft." + className);
            continue;
          }
          catch (NoSuchMethodException e) {
            System.err.println("**WARNING: class dft." + className + " does "
                               + "not contain a getFileExtension() method.");
            continue;
          }
          catch (InstantiationException e) {
            System.err.println("**WARNING: could not create an instance of "
                               + "class dft." + className);
            continue;
          }
          /* with Java 7, these next two catch blocks can be combined (and they
             should) */
          catch (InvocationTargetException e) {
            System.err.println("**WARNING: could not invoke getFileExtension()"
                               + " method from class dft." + className);
            continue;
          }
          catch (IllegalAccessException e) {
            System.err.println("**WARNING: could not invoke getFileExtension()"
                + " method from class dft." + className);
            continue;
          }

          System.out.println(className);
        }
        else if (file.indexOf("DataWriter") > 0) {
          System.out.println(file);
        } 
      }
    }
  }

ClassNotFoundException is NOT thrown, but the result of forName() is null. The documentation says nothing about returning null.

Does anyone have any clue as to why this is happening? I tested the call of forName() in another project that doesn't use a package name (the code above is in a package named "dft"), and that one worked fine. I'm thinking that has something to do with it. The classpath is fine as well--the .class files are in ...bin/dft and the classpath contains .../bin. I even tried adding the .../bin/dft directory explicitly in the classpath just in case, and it still returns null.

Answer 1

You are assigning the value returned by forName to

        readerclass    (lowercase C)

but calling getMethod from

        readerClass    (uppercase C)

which probably is an uninitialized field.

Java is case-sensitive.