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

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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

Best Answer

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

Related Solutions

Ruby – How to search a folder and all of its subfolders for files of a certain type

Try this:

Dir.glob("#{folder}/**/*.pdf")

which is the same as

Dir["#{folder}/**/*.pdf"]

Where the folder variable is the path to the root folder you want to search through.

Iterate through folders, then subfolders and print filenames with path to text file

Charles' answer is good, but can be improved upon to increase speed and efficiency. Each item produced by os.walk() (See docs) is a tuple of three items. Those items are:

The working directory
A list of strings naming any sub-directories present in the working directory
A list of files present in the working directory

Knowing this, much of Charles' code can be condensed with the modification of a forloop:

import os

def list_files(dir):
    r = []
    for root, dirs, files in os.walk(dir):
        for name in files:
            r.append(os.path.join(root, name))
    return r

Best Answer

Related Solutions

Ruby – How to search a folder and all of its subfolders for files of a certain type

Iterate through folders, then subfolders and print filenames with path to text file

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