In this Java tutorial, you will learn how to get the list of files and sub-directories in a given folder, with examples.
Java – Filter files or sub-directories in a directory
You can get the list of files and sub-directories in a given folder using Java. We can also filter the list based on extension or a specific condition.
In this Java Tutorial, we shall learn how to perform the following tasks.
- Extract list of files and directories in a folder using java
- Extract list of files belonging to specific file type
- Extract list of files belonging to specific file type, present in the folder and its sub folders/directories
Extract list of files and sub-directories in a directory
Follow these steps to extract the names of files and sub directories in a given directory.
Step 1 : Specify the folder. In this example, “sample” is the folder name placed at the root to the project.
File folder = new File("sample"); Step 2 : Get the list of all items in the folder.
File[] listOfFiles = folder.listFiles();
Step 3 : Check if an item in the folder is a file.
listOfFiles[i].isFile()
Step 4 : Check if an item in the folder is a directory.
listOfFiles[i].isDirectory()
Complete program that lists the files and directories in a folder is given below.
ListOfFilesExample.java
import java.io.File;
import java.util.ArrayList;
import java.util.List;
/**
* Program that gives list of files or directories in a folder using Java
*/
public class ListOfFilesExample {
public static void main(String[] args) {
List files = new ArrayList<>();
List directories = new ArrayList<>();
File folder = new File("sample");
File[] listOfFiles = folder.listFiles();
for (int i = 0; i < listOfFiles.length; i++) {
if (listOfFiles[i].isFile()) {
files.add(listOfFiles[i].getName());
} else if (listOfFiles[i].isDirectory()) {
directories.add(listOfFiles[i].getName());
}
}
System.out.println("List of files :\n---------------");
for(String fName: files) System.out.println(fName);
System.out.println("\nList of directories :\n---------------------");
for(String dName: directories) System.out.println(dName);
}
} The sample folder and its contents are as shown in the below picture :
When the program is run, output to the console would be as shown below.
Output
List of files : --------------- html_file_1.html text_file_1.txt text_file_3.txt text_file_2.txt List of directories : --------------------- directory_1 directory_2
Get list of files of specific extension from the directory
Follow these steps.
Step 1 : Specify the folder.
File folder = new File("sample"); Step 2 : Get the list of all items in the folder.
File[] listOfFiles = folder.listFiles();
Step 3 : Check if an item in the folder is a file.
listOfFiles[i].isFile()
Step 4 : Check if the file belong to specified file-type.
Check the extension of the filename with String.endsWith(suffix)
listOfFiles[i].getName().endsWith(fileExtension)
Complete program to get the list of files, that belong to a specified extension type is shown below.
ListOfFilesExample.java
import java.io.File;
import java.util.ArrayList;
import java.util.List;
public class ListOfFilesExample {
public static void main(String[] args) {
List files = new ArrayList<>();
List directories = new ArrayList<>();
String fileExtension = ".txt";
File folder = new File("sample");
File[] listOfFiles = folder.listFiles();
for (int i = 0; i < listOfFiles.length; i++) {
if (listOfFiles[i].isFile()) {
if(listOfFiles[i].getName().endsWith(fileExtension)){
files.add(listOfFiles[i].getName());
}
}
}
System.out.println("List of .txt files :\n--------------------");
for(String fName: files) System.out.println(fName);
}
} When the program is run, Output to the console would be as shown below.
Output
List of .txt files : -------------------- text_file_1.txt text_file_3.txt text_file_2.txt
Get list of files with specific extension from the directory and its sub-directories
Follow these steps.
Step 1 : Specify the folder.
File folder = new File("D:"+File.separator+"Arjun"+File.separator+"sample"); Step 2 : Get the list of all items in the folder.
File[] listOfFiles = folder.listFiles();
Step 3 : Check if an item in the folder is a file.
listOfFiles[i].isFile()
Step 4 : Check if the file belong to specified file-type.
Check the extension of the filename with String.endsWith(suffix)
listOfFiles[i].getName().endsWith(fileExtension)
Step 5 : Check if an item in the folder is a directory.
listOfFiles[i].isDirectory()
Step 6 : Get the list of files (beloging to specific file-type) recursively from all the sub-directories.
The complete program is given below.
FileListExtractor.java
import java.io.File;
import java.util.ArrayList;
import java.util.List;
public class FileListExtractor {
List allTextFiles = new ArrayList();
String fileExtension = ".txt";
public static void main(String[] args) {
FileListExtractor folderCrawler = new FileListExtractor();
folderCrawler.crawlFold("sample");
System.out.println("All text files in the folder \"sample\" and its sub directories are :\n---------------------------------------------------------------");
for(String textFileName:folderCrawler.allTextFiles){
System.out.println(textFileName);
}
}
public void crawlFold(String path){
File folder = new File(path);
File[] listOfFiles = folder.listFiles();
for (int i = 0; i < listOfFiles.length; i++) {
if (listOfFiles[i].isFile()) {
if(listOfFiles[i].getName().endsWith(fileExtension)){
allTextFiles.add(listOfFiles[i].getName());
}
} else if (listOfFiles[i].isDirectory()) {
// if a directory is found, crawl the directory to get text files
crawlFold(path+File.separator+listOfFiles[i].getName());
}
}
}
} When the program is run, output to the console is
Output
All text files in the folder "sample" and its sub directories are : --------------------------------------------------------------- text_file_2_1.txt text_file_1_1.txt text_file_2_1.txt text_file_1_1.txt text_file_2_2.txt text_file_1_2.txt text_file_1.txt text_file_3.txt text_file_2.txt
Conclusion
In this Java Tutorial, we learned how to list all the files and sub-directories in a given folder.