我想从文件中读取，程序从命令行参数中获取文件名（文件也是java文件），然后使用 java.nio.file.Files 以及 java.nio.file.Path 也许 吧。我应该读文件名使用的主要功能我不知道怎么做，有什么帮助plz？这实际上是我第一次用java编写代码，所以我遇到了很多困难

package firtJavaCode;

import java.io.*; 
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.StringTokenizer;
import java.lang.String ;

public class ReadFromFile {

    public static void main(String[] args) {
        try {
            //String filePath = "";   // here is my problem i don't know how to read from a giving file
            String line;
            BufferedReader br = new BufferedReader(new FileReader(filePath));
            int lineNumber = 0;
            while ((line = br.readLine()) != null) {
                lineNumber++;
                if  (line.contains("//")) {
                     StringTokenizer st1 =  new StringTokenizer(line, "//");            
                     System.out.println(st1.nextToken()); 
                }

                // i still didn't complete the code , just want to figure how to read from file first
            }
        }catch (Exception e) {
            System.out.println(e);
        }
    }
}