Java8 -> Java7 conversion File.walk

import java.io.File;
import java.util.ArrayList;
import java.util.List;

public class FileWalker {
    public static List<File> walk(String path) {
        List<File> fileList = new ArrayList<>();
        File root = new File(path);
        File[] files = root.listFiles();
        
        if (files != null) {
            for (File file : files) {
                if (file.isDirectory()) {
                    fileList.addAll(walk(file.getAbsolutePath()));
                } else {
                    fileList.add(file);
                }
            }
        }
        
        return fileList;
    }
}