Java在讀取檔案內容的時候,如何判斷出空白行的操作

import java.util.*;
import java.util.Map.Entry;
import java.io.*;
 
public class choosePath {
private static ArrayList arrayListOfChoosedPath=new ArrayList();
 private static ArrayList arrayListOfMustThoughNode=new ArrayList();
 private static ArrayList arrayListOfMustThoughEdge=new ArrayList();
 private static ArrayList arrayListOfCanNotThoughEdge=new ArrayList();
 
 private static int needOfNode;
 
 public static void main(String[] args) throws IOException {
 
 //sumCol變數用於記錄資料集中邊的數量
 int sumCol=0;
 BufferedReader bfr2 = new BufferedReader(new FileReader(
  "C://Users//Administrator//Desktop//text//case.txt"));
 bfr2.readLine();
 bfr2.readLine();
 while(!bfr2.readLine().equals("")){
  sumCol++;
 }
 System.out.println("tempcol="+sumCol);
 
 
 String tempMustThoughNode=null;
 while(!(tempMustThoughNode=bfr2.readLine()).equals("")){
  System.out.println(tempMustThoughNode);
  arrayListOfMustThoughNode.add(tempMustThoughNode);
 }
 while(!(tempMustThoughNode=bfr2.readLine()).equals("")){
  System.out.println(tempMustThoughNode);
  arrayListOfMustThoughEdge.add(tempMustThoughNode.split(" ")[0]);
  arrayListOfMustThoughEdge.add(tempMustThoughNode.split(" ")[1]);
 }
 
 while((tempMustThoughNode=bfr2.readLine())!=null){
  System.out.println(tempMustThoughNode);
  arrayListOfCanNotThoughEdge.add(tempMustThoughNode.split(" ")[0]);
  arrayListOfCanNotThoughEdge.add(tempMustThoughNode.split(" ")[1]);
 }
 bfr2.close();
}
}

public static String txt2String(File file) {
    StringBuilder result = new StringBuilder();
    try {
      BufferedReader br = new BufferedReader(new FileReader(file));//構造一個BufferedReader類來讀取檔案
      String s = null;
      while ((s = br.readLine()) != null) {//使用readLine方法，一次讀一行
        result.append(System.lineSeparator() + s);
      }
      br.close();
    } catch (Exception e) {
      e.printStackTrace();
    }
    return result.toString();
  }
 
  public static void main(String[] args) {
    File file = new File("C:UsersAdministratorDesktop檔名.txt");
    String s = txt2String(file);
    String[] split = s.split("r?n");
    for (String s1 : split) {
      if (s1.length() > 0) {
        String[] split1 = s1.split("s+");
        for (String s2 : split1) {
          if (s2.length() > 0) {
            System.out.println(s2);
          }
        }
      }
 
    }
  }