How do I iterate through the files in a directory in Java?
You can use File#isDirectory()
to test if the given file (path) is a directory. If this is true
, then you just call the same method again with its File#listFiles()
outcome. This is called recursion.
Here's a basic kickoff example:
package com.stackoverflow.q3154488;
import java.io.File;
public class Demo {
public static void main(String... args) {
File dir = new File("/path/to/dir");
showFiles(dir.listFiles());
}
public static void showFiles(File[] files) {
for (File file : files) {
if (file.isDirectory()) {
System.out.println("Directory: " + file.getAbsolutePath());
showFiles(file.listFiles()); // Calls same method again.
} else {
System.out.println("File: " + file.getAbsolutePath());
}
}
}
}
Note that this is sensitive to StackOverflowError
when the tree is deeper than the JVM's stack can hold. If you're already on Java 8 or newer, then you'd better use Files#walk()
instead which utilizes tail recursion:
package com.stackoverflow.q3154488;
import java.io.File;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
public class DemoWithJava8 {
public static void main(String... args) throws Exception {
Path dir = Paths.get("/path/to/dir");
Files.walk(dir).forEach(path -> showFile(path.toFile()));
}
public static void showFile(File file) {
if (file.isDirectory()) {
System.out.println("Directory: " + file.getAbsolutePath());
} else {
System.out.println("File: " + file.getAbsolutePath());
}
}
}
If you are using Java 1.7, you can use java.nio.file.Files.walkFileTree(...)
.
For example:
public class WalkFileTreeExample {
public static void main(String[] args) {
Path p = Paths.get("/usr");
FileVisitor<Path> fv = new SimpleFileVisitor<Path>() {
@Override
public FileVisitResult visitFile(Path file, BasicFileAttributes attrs)
throws IOException {
System.out.println(file);
return FileVisitResult.CONTINUE;
}
};
try {
Files.walkFileTree(p, fv);
} catch (IOException e) {
e.printStackTrace();
}
}
}
If you are using Java 8, you can use the stream interface with java.nio.file.Files.walk(...)
:
public class WalkFileTreeExample {
public static void main(String[] args) {
try (Stream<Path> paths = Files.walk(Paths.get("/usr"))) {
paths.forEach(System.out::println);
} catch (IOException e) {
e.printStackTrace();
}
}
}
Check out the FileUtils class in Apache Commons - specifically iterateFiles:
Allows iteration over the files in given directory (and optionally its subdirectories).