Create a huge dummy file in Java in an instant

To create a file of arbitrary size without really ‘writing it’, which can take quite some time for huge files, you can use java.io.RandomAccessFile.

import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;

public class RunnableExample {

    public static void main(String[] args) throws IOException {
        // Create a file with 1 GB size
        createFileWithSize(new File("/Users/kaimechel/temp"), "dummyFile", 1L * 1024L * 1024L * 1024L);
    }

    public static File createFileWithSize(File parentFolder, String filename, long size) throws IOException {
        File file = new File(parentFolder, filename);
        try (RandomAccessFile raf = new RandomAccessFile(file, "rw")) {
            raf.setLength(size);
        }
        return file;
    }
}