Learn to use Java 8 APIs such as Files.list() and DirectoryStream to list all files present in a directory, including hidden files, recursively.
For using external iteration (for loop) use
DirectoryStream. For using Stream API operations (map, filter, sorted, collect), useFiles.list()instead.
1. Files.list() – Iterate over all files and sub-directories
Java example to iterate over a directory and get the List<File> using Files.list() method.
import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;
import java.util.stream.Collectors;
public class IterateDirectoryExample {
public static void main(String[] args) {
String dirLocation = "C:/temp";
try {
List<File> files = Files.list(Paths.get(dirLocation))
.map(Path::toFile)
.collect(Collectors.toList());
files.forEach(System.out::println);
} catch (IOException e) {
// Error while reading the directory
}
}
}
Program Output:
C:\temp\filename1.txt C:\temp\directory1 C:\temp\filename2.txt C:\temp\Employee.java
2. Files.list() – List only files excluding sub-directories
Use the filter expression Files::isRegularFile to check if a file is normal file, and not any directory.
String dirLocation = "C:/temp"; List<File> files = Files.list(Paths.get(dirLocation)) .filter(Files::isRegularFile) .map(Path::toFile) .collect(Collectors.toList()); files.forEach(System.out::println);
Program Output:
C:\temp\filename1.txt C:\temp\filename2.txt C:\temp\Employee.java
To list files in a different directory, we can replace "." with the full path of the directory we desire.
3. Files.newDirectoryStream() – List all files and sub-directories
Java provides a more flexible way of traversing a directory content using Files.newDirectoryStream().
Please note that if we’re working with a large directory, then using
DirectoryStreamactually make code faster.
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
public class IterateDirectoryExample {
public static void main(String[] args) {
String dirLocation = "C:/temp";
try {
for (Path path : Files.newDirectoryStream(Paths.get(dirLocation))) {
path = path.normalize();
System.out.println(path.getFileName());
}
} catch (IOException e) {
// Error while reading the directory
}
}
}
Program Output:
C:\temp\filename1.txt C:\temp\directory1 C:\temp\filename2.txt C:\temp\Employee.java
4. Files.newDirectoryStream() – Iterate only files excluding sub-directories
To loop through only the files and excluding all the sub-directories from the stream, use path filter isFile() as the second argument to the newDirectoryStream() constructor.
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
public class IterateDirectoryExample {
public static void main(String[] args) {
String dirLocation = "C:/temp";
try {
for (Path path : Files.newDirectoryStream(Paths.get(dirLocation),
path -> path.toFile().isFile())) {
path = path.normalize();
System.out.println(path.getFileName());
}
} catch (IOException e) {
// Error while reading the directory
}
}
}
Program Output:
C:\temp\filename1.txt C:\temp\filename2.txt C:\temp\Employee.java
5. List of all files of certain extention only
To get the list of all files of certain extensions only, use two predicates Files::isRegularFile and path.toString().endsWith(".java") together.
With the above predicate, we are listed all .java files in a folder.
import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;
import java.util.stream.Collectors;
public class IterateDirectoryExample {
public static void main(String[] args) {
String dirLocation = "C:/temp";
try {
List<File> files = Files.list(Paths.get(dirLocation))
.filter(Files::isRegularFile)
.filter(path -> path.toString().endsWith(".java"))
.map(Path::toFile)
.collect(Collectors.toList());
files.forEach(System.out::println);
} catch (IOException e) {
// Error while reading the directory
}
}
}
Program Output:
C:\temp\Employee.java
6. Finding all hidden files in a directory
To find all the hidden files, we can use filter expression file -> file.isHidden() in any of above example.
List<File> files = Files.list(Paths.get(dirLocation)) .filter(path -> path.toFile().isHidden()) .map(Path::toFile) .collect(Collectors.toList());
In the above examples, we learn to use the java 8 APIs loop through the files in a directory recursively using various search methods. Feel free to modify the code and play with it.
Happy Learning !!
References:
DirectoryStream
Files.list() method
Hi,
how to apply filter to get the list of files created between two dates.
Could you please suggest on this.
Files.newDirectoryStream(Paths.get(directory),
path -> path.toFile().lastModified() > sd.getTime() && path.toFile().lastModified() < ed.getTime());
Alex B, that code does not demonstrate what list the filenames go to. Where is the list variable ?
Here is the code for reading filename and store them in list.
List fileNamesList = new ArrayList(); Files.newDirectoryStream(Paths.get(dir), path -> path.toString().endsWith(".java")).forEach(filePath -> fileNamesList.add(filePath.toString()));I appreciate the post.
But the code in “Find all hidden files in directory” section gives syntax error.
And, its sad that you didn’t tell how to capture the file names in a list or something else (will be helpful for the people who are learning java 8). In real world, we don’t need to read the file names just to sysout.
Here is the code for reading file names and store them in list.
You’re actually better off doing something like this:
Files.list(Paths.get(dir)) .map(Path::toFile) .map(File::getAbsolutePath) .collect(Collectors.toList())Which allows you to use the streams api to transform/filter the list before you collect it.
Files.list(Paths.get(dir)) .map(Path::toAbsolutePath) .collect(Collectors.toList())nice code