List All Files in a Directory in Java

In this section, we are going to learn how one can list all the files that are present in a directory. Note that a directory may contain a subdirectory, and that subdirectory may contain some files. We have to list these files, too, as these files are also part of the main directory. However, for the sake of simplicity, we will first look at the scenario where subdirectories are not present.

Directory without having Sub-directories

It means a folder is only containing files. Steps to print the files of a directory are mentioned below.

Step 1: Create a File Object for the directory.

Step 2: Obtain the array of files of that directory.

Step 3: Recursively, print the name of files (with extension) one by one.

Implementation

The following code prints the file names mentioned in the folder called Documents. The following snapshot shows the files present in the folder named Documents.

FileName: DisplayFileExample.java

// import statement
import java.io.File;
public class DisplayFileExample
{
public void printFileNames(File[] a, int i, int lvl)
{
// base case of the recursion
// i == a.length means the directory has 
// no more files. Hence, the recursion has to stop
if(i == a.length)
{
return;
}
// checking if the encountered object is a file or not
if(a[i].isFile())
{
System.out.println(a[i].getName());
}
// recursively printing files from the directory
// i + 1 means look for the next file
printFileNames(a, i + 1, lvl);
}
// Main Method
public static void main(String[] argvs)
{
// Providing the full path for the directory
String path = "E:\\Documents";
// creating a file object
File fObj = new File(path);
// creating on object of the class DisplayFileExample
DisplayFileExample obj = new DisplayFileExample();
if(fObj.exists() && fObj.isDirectory())
{
// array for the files of the directory pointed by fObj
File a[] = fObj.listFiles();
// display statements
System.out.println("= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =");
System.out.println("Displaying Files from the directory : " + fObj);
System.out.println("= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =");
// Calling the method
obj.printFileNames(a, 0, 0);
}
}
}

Output:

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
Displaying Files from the directory: E:\Documents
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
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The Normal Forms2.ppt

Directory with Subdirectories

It means a folder contains files as well as subfolders. Steps to print the files of a directory and its subdirectory are mentioned below.

Step 1: Create a File Object for the directory.

Step 2: Obtain the array of files and subdirectory of that directory.

Step 3: If array[j] is a file, then display the file name and recursively go to the next element of the array[j].

Step 4: If array[j] is a directory, then display then directory name, and repeat from step 2.

Implementation

We have already seen the contents of the folder named Documents. Now, we create some folders inside Documents and store number of files in it. Observe the following snapshots.

The above snapshot shows the Documents directory has 3 sub-directories named (New folder - 1, New folder - 2, New folder - 3).

The following snapshot shows the content of the folder named New folder - 1

The following snapshot shows the content of the folder named New folder - 2

The following snapshot shows the content of the folder named New folder - 3

After the creation of folders, we can write the code on the basis of the steps defined above.

FileName: DisplayFileExample1.java

// import statement
import java.io.File;
public class DisplayFileExample1
{
public void printFileNames(File[] a, int i, int lvl)
{
// base case of the recursion
// i == a.length means the directory has 
// no more files. Hence, the recursion has to stop
if(i == a.length)
{
return;
}
// tabs for providing the indentation
// for the files of sub-directory
for (int j = 0; j < lvl; j++)
{
System.out.print("\t");
}
// checking if the encountered object is a file or not
if(a[i].isFile())
{
System.out.println(a[i].getName());
}
// for sub-directories
else if(a[i].isDirectory())
{
System.out.println("[" + a[i].getName() + "]");
// recursion for sub-directories
printFileNames(a[i].listFiles(), 0, lvl + 1);
}
// recursively printing files from the directory
// i + 1 means look for the next file
printFileNames(a, i + 1, lvl);
}
// Main Method
public static void main(String[] argvs)
{
// Providing the full path for the directory
String path = "E:\\Documents";
// creating a file object
File fObj = new File(path);
// creating on object of the class DisplayFileExample1
DisplayFileExample1 obj = new DisplayFileExample1();
if(fObj.exists() && fObj.isDirectory())
{
// array for the files of the directory pointed by fObj
File a[] = fObj.listFiles();
// display statements
System.out.println("= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =");
System.out.println("Displaying Files from the directory: " + fObj);
System.out.println("= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =");
// Calling the method
obj.printFileNames(a, 0, 0);
}
}
}

Output:

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
Displaying Files from the directory: E:\Documents
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
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