This method allow you to create file in specific folder under your project root. If you want to to save it somewhere on your computer, you can use "user.home" instead of "user.dir"

createFileInDirectory.java

// get System properties :
            Properties properties = System.getProperties();
            // get Operating System home directory
            String home = properties.get("user.dir").toString();
            // get Operating System separator
            String separator = properties.get("file.separator").toString();
            // your directory name
            String directoryName = "directoryName";
            // your file name
            String fileName = "filename";
            // create your directory Object (wont harm if it is already there ...
            // just an additional object on the heap that will cost you some bytes
            File dir = new File(home+separator+directoryName);
            //  create a new directory, will do nothing if directory exists
            dir.mkdir();
            // create your file Object
            File output = new File(dir,fileName);