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Traversing directory in Java using BFS

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Given a directory, print all files and folders present in directory tree rooted with given directory. We can iteratively traverse directory in BFS using below steps. We create an empty queue and we first enqueue given directory path. We run a loop while queue is not empty. We dequeue an item from queue. If the popped item is a directory, get list of all files and directories present in it, add each directory to the queue. If the popped item is a file, we print its name. 


// Java program to print all files/directories
// present in a directory.
import java.util.LinkedList;
import java.util.Queue;
class FileUtils {
    public static void printDirsFiles(String inputDir)
        /* make a queue to store files and directories */
        Queue<File> queue = new LinkedList<>();
        queue.add(new File(inputDir));
        /* loop until queue is empty -*/
        while (!queue.isEmpty()) {
            /* get next file/directory from the queue */
            File current = queue.poll();
            File[] fileDirList = current.listFiles();
            if (fileDirList != null) {
                /* Enqueue all directories and print
                all files. */
                for (File fd : fileDirList) {
                    if (fd.isDirectory())
    /* Iterative function to traverse given
    directory in Java using BFS*/
    public static void main(String[] args)
        String inputDir = "C:\\Programs";

Time Complexity: O(n), where n is the number of files and folders present in directory tree rooted with given directory
Auxiliary Space: O(n)

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Last Updated : 21 Dec, 2022
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