输出是一个空白的文本文件

Question

你能解释为什么我的2方法mergeFile（）和mergeData（）不起作用，当我运行它给我一个空白的文本文件。我真的不明白为什么.....下面是我的代码：

String dirName, fileName; 

public MergeFile(String dirName, String fileName){ 
    this.dirName = dirName; 
    this.fileName = fileName; 
} 

public static void main(String [] args){ 
    MergeFile mf = new MergeFile("C:\\Users\\Shine\\Desktop", "C:\\Users\\Shine\\Desktop\\trung.txt"); 
    mf.mergeData(); 
} 

public void mergeData(){ 
    for (int i = 0; i < createData().size(); i++){ 
     FileReader fr; 
     BufferedReader br; 
     FileWriter fw; 
     BufferedWriter bw = null; 
     try{ 
      fr = new FileReader(createData().get(i)); 
      br = new BufferedReader(fr); 

      fw = new FileWriter(fileName); 
      bw = new BufferedWriter(fw); 

      String line; 
      while ((line = br.readLine()) != null){ 
       bw.write(line); 
      } 
      br.close(); 
     }catch(IOException exp){ 
      exp.printStackTrace(); 
     }finally{ 
      try { 
       if (bw != null){ 
        bw.flush(); 
        bw.close(); 
       } 
      }catch(IOException exp){ 
       exp.printStackTrace(); 
      } 
     } 
    } 
} 

我createData方法：

public ArrayList<File> createData(){ 
    File directory = new File(dirName); 
    ArrayList<File> file = new ArrayList<>(); 
    if (directory.isDirectory()){ 
     for (int i = 0; i < directory.listFiles().length; i++){ 
      if (directory.listFiles()[i].getName().endsWith(".txt")){ 
       file.add(directory.listFiles()[i]); 
      } 
     } 
     return file; 
    }else{ 
     return null; 
    } 
} 

我mergeFile方法：

public void mergeFile(){ 
    for (int i = 0; i < createData().size(); i++){ 
     try{ 
      FileInputStream fis = new FileInputStream(createData().get(i)); 
      FileOutputStream fos = new FileOutputStream(fileName); 

      int counter; 

      while((counter = fis.read()) != -1){ 
       System.out.println(counter); 
       //fos.write(counter); 
      } 
      fos.flush(); 
      fos.close(); 
     }catch(IOException exp){ 
      exp.printStackTrace(); 
     } 
    } 
} 

Answer 1

移动声明

FileReader fr; 
BufferedReader br; 
FileWriter fw; 
BufferedWriter bw = null; 

环外。

Answer 2

使用flush()函数内部循环本身后写功能