Recursive method to search through folder tree and find specific file types

问题

So I am writing a code that locates certain information on Protein databases. I know that a recursive folder search is the best possible way to locate these files, but I am very new to this language and have been told to write in Java (I normally do C++)

SO this being said, what method would i use to:

First: Locate the folder on desktop
Second: Open each folder and that folders subfolders
Third: Locate files that end with the ".dat" type (because these are the only files that have stored the Protein information

Thanks for any and all help you can provide

回答1:

java.io.File is "An abstract representation of file and directory pathnames"
File.listFiles provides a listing of all the files contained within the directory (if the File object represents a directory)
File.listFiles(FileFilter) provides you with the ability to filter a file list based on your needs

So, with that information...

You would specify a path location with something like...

File parent = new File("C:/path/to/where/you/want");

You can check that the File is a directory with...

if (parent.isDirectory()) {
    // Take action of the directory
}

You can list the contents of the directory by...

File[] children = parent.listFiles();
// This will return null if the path does not exist it is not a directory...

You can filter the list in a similar way...

File[] children = parent.listFiles(new FileFilter() {
        public boolean accept(File file) {
            return file.isDirectory() || file.getName().toLowerCase().endsWith(".dat");
        }
    });
// This will return all the files that are directories or whose file name ends
// with ".dat" (*.dat)

Other useful methods would include (but not limited to)

File.exists to test that the file actually exists
File.isFile, basically instead of saying !File.isDirectory()
File.getName(), returns the name of the file, excluding it's path
File.getPath() returns the path and name of the file. This can be relative, so be careful, see File.getAbsolutePath and File.getCanonicalPath to resolve this.
File.getParentFile which gives you access to the parent folder

回答2:

Something like this would do the trick:

public static void searchForDatFiles(File root, List<File> datOnly) {
    if(root == null || datOnly == null) return; //just for safety   
    if(root.isDirectory()) {
        for(File file : root.listFiles()) {
            searchForDatFiles(file, datOnly);
        }
    } else if(root.isFile() && root.getName().endsWith(".dat")) {
        datOnly.add(root);
    }
}

After this method returns, the List<File> passed to it will be filled with the .dat files of your directory, and all subdirectories (if i'm not mistaken).

回答3:

You should have a look at the Java File APIs. In particular you should look at the listFiles method and write FileFilter that selects directories and, of course, the files you're interested into.

A method that will return you all the files matching your criteria (Given that you implement the FileFilter) is this:

List<File> searchForFile(File rootDirectory, FileFilter filter){
    List<File> results = new ArrayList<File>();
    for(File currentItem : rootDirectory.listFiles(filter){
      if(currentItem.isDirectory()){
          results.addAll(searchForFile(currentItem), filter)
      }
      else{
          results.add(currentItem);
      }
    }
    return results;
}

回答4:

use recursive foldr search and use function endsWith() to find the .bat file then you can use any String function to locate your requires information.

来源：https://stackoverflow.com/questions/12656569/recursive-method-to-search-through-folder-tree-and-find-specific-file-types

标签

java

recursion