How do you read in a file from a subdirectory in Java?

Question

I have a Folder named Class and its two subdirectories are Lectures and Grades, and within those two subdirectories are txt files. How do I access the subdirectories (and maybe other subdirectories of the subdirectories Lectures and Grades)from the main directory - Class? I know I can use the absolute path in the code, but I would like to start from the starting folder, Class. So far, I have this as my code:

public class Test {
    public static void main(String[] args) {
        File directory = new File("/Users/Desktop/Class");
        File[] folder = directory.listFiles();
        for (File aFile : folder) {
            // Stuck here...
        }
    }
}

Sorry.. I'm new to Java..

Answer 1

You can recursively call the method to read the file in sub directories

public static void main(String[] args) {
    File currentDir = new File("/Users/Desktop/Class"); // current directory
    displayDirectoryFiles(currentDir);
}

public static void displayDirectoryFiles(File dir) {
    try {
        File[] files = dir.listFiles();
        for (File file : files) {
            if (file.isDirectory()) {
                System.out.println("directory:" + file.getCanonicalPath());
                displayDirectoryContents(file);
            } else {
                System.out.println("     file:" + file.getCanonicalPath());
            }
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

Handle the exception properly, currently just printing stacktrace

Answer 2

// Recursive Java program to print all files 
// in a folder(and sub-folders) 

import java.io.File; 

public class GFG 
{ 
    static void RecursivePrint(File[] arr,int index,int level) 
    { 
        // terminate condition 
        if(index == arr.length) 
            return; 

        // tabs for internal levels 
        for (int i = 0; i < level; i++) 
            System.out.print("\t"); 

        // for files 
        if(arr[index].isFile()) 
            System.out.println(arr[index].getName()); 

        // for sub-directories 
        else if(arr[index].isDirectory()) 
        { 
            System.out.println("[" + arr[index].getName() + "]"); 

            // recursion for sub-directories 
            RecursivePrint(arr[index].listFiles(), 0, level + 1); 
        } 

        // recursion for main directory 
        RecursivePrint(arr,++index, level); 
    } 

    // Driver Method 
    public static void main(String[] args) 
    { 
        // Provide full path for directory(change accordingly) 
        String maindirpath = "C:\\Users\\Gaurav Miglani\\Desktop\\Test"; 

        // File object 
        File maindir = new File(maindirpath); 

        if(maindir.exists() && maindir.isDirectory()) 
        { 
            // array for files and sub-directories 
            // of directory pointed by maindir 
            File arr[] = maindir.listFiles(); 

            System.out.println("**********************************************"); 
            System.out.println("Files from main directory : " + maindir); 
            System.out.println("**********************************************"); 

            // Calling recursive method 
            RecursivePrint(arr,0,0); 
    } 
    } 
} 

Answer 3

have you looked at this answer: Java, List only subdirectories from a directory, not files ?

also this could be a solution, there are several ways: http://zetcode.com/articles/javalistdirectory/

Answer 4

In addition to Ros5292 answer, this can be achieven using Apache Commons IO library.

public void iterateFilesAndDirectoriesUsingApacheCommons() {
        Iterator it = FileUtils.iterateFilesAndDirs(new File("/Users/Desktop/"), TrueFileFilter.INSTANCE, TrueFileFilter.INSTANCE);
        while (it.hasNext()) {
            System.out.println(((File) it.next()).getName());
        }
    }