How can I use non-static func in a static func?

Question

Hello guys,
I have a func processFiles which is static, i wanna use a func from another class FileData in processFile func and i dnt wanna make processFile non-static, what should i do?
my code:
public class Library {
     private FileData file = new FileData();
     public static void main(String[] args){
        try{
             Library lib = new Library();
              lib.processFiles(args);
        catch(IOException e)
             System.err.println("IOException occurred in main.");
               System.exit(0);
     @SuppressWarnings("unchecked")
     public  static void processFiles(String[] fileNames) throws IOException {
          file.getMaterial();// I get error here;
class FileData{
    getMaterila() {}
}

Answer 1

1) it's not "func", it's "method".
2) Create a FileData instance and call the method on that
3) Read the basic tutorials about what "static" means, and put the error message into Google.