Reading files using wildcard character

Question

Hi Everyone,
I currently implemented a servlet that reads contents of a specific directory using File class:
File contens = new File(directory_path);
After this I would simply call contents.list(), which would list all of the files in that particular directory. And this works fine but I need to filter some of the files out so I came up with a solution of using a wildcard character:
File contents = new File(directory_path + "SomeString" + "*");
I would assume that this should give me all of the file names that begin with "SomeString" but it does not work that well. Instead I get null trying to instantiate a new instance of a File object and NullPointerException when I try to call list() method on it.
How can I read directory contents if I want only certain file names that begin with "SomeString" for example.
Any help will be greatly appreciated!
Thanks in advance,
Y.M.

Answer 1

You can create a FilenameFilter and use it like this:
            myFilenameFilter filter=new myFilenameFilter();
            String[] dirArray=new File(myPath).list(filter);
   class myFilenameFilter implements FilenameFilter {
      public boolean accept(File dir, String name) {
         if (name.startsWith(SomeString)) return true; else return false;
}where SomeString is a globally accessible String.
V.V.