Traversing Folders and Files Recursively

Both files and folders are represented as File object in the java.io package. We are recognizing if an object is a file by using the method "isFile()" and a folder with the method "isDirectory()".

import java.io.File;

public class FilesFoldersTraversal {

 private final char SEPARATOR = File.separatorChar;
 private File originalFile;
 private File referencedFile;
 private String pad = null;
 private String absolutePathOriginalFile = null;

 public FilesFoldersTraversal(String inputFileString) {
  File inputFile = new File(inputFileString);
  originalFile = inputFile;
  referencedFile = inputFile;
  absolutePathOriginalFile = originalFile.getAbsolutePath();
 }

 public void traverseFilesFolders () {
  traverseFilesFolders(referencedFile);
 }

 private void traverseFilesFolders(File referencedFile){ 
  if (referencedFile.isDirectory()){
   pad = getPadding(referencedFile);
   processFolders(referencedFile);
  }
  else if (referencedFile.isFile()){
   processFiles(referencedFile);
  }
 }

 private void processFolders(File referencedFile){
  System.out.println(pad + "Folder: " + referencedFile.getName());
  File listFiles[] = referencedFile.listFiles();
  for(File singleFile : listFiles){
   traverseFilesFolders(singleFile);
  }
 }

 private void processFiles(File referencedFile){
  System.out.println(pad  + "  " + "File: " + referencedFile.getName());
 }

 private String getPadding(File referencedFile){
  String padding = ""; 
  String fileAbsolutePath = referencedFile.getAbsolutePath();  
  String filePathSubString = fileAbsolutePath.substring(absolutePathOriginalFile.length(), fileAbsolutePath.length());

  int index = 0;
  int subStringLength = filePathSubString.length();
  while (index < subStringLength) {
   if (filePathSubString.charAt(index) == SEPARATOR){
    padding += "  ";
   }
   index++;
  }

  return padding;
 }

 public static void main(String[] args) {
  FilesFoldersTraversal fft = new FilesFoldersTraversal("/Users/YOUR_USER_NAME/Documents");
  fft.traverseFilesFolders();
 }

}

There are many interesting things you can do with the example shown. You may add a few lines of codes to compile a list of files of a specific file extension, for example ".txt" or ".class".