The resource FileWriter of a try-with-resources statement cannot be assigned-CodePudding

I need to split a FileWriter into multiple partitioned files using "try-with-resources" technique. But when I use "try-with-resources", I can't recreate the FileWriter and BufferWriter in a different file. I'm trying to solve some sonar issues and "try-with-resources" is a rule to follow.

Does anyone have an idea to solve it?

Thanks

....


try (InputStream fis=new FileInputStream(sArquivo);
BufferedReader br=new BufferedReader(new InputStreamReader(fis)); 
FileWriter fw = new FileWriter(sNomeArquivoDestino);
BufferedWriter bw = new BufferedWriter(fw)) {                
     String vLinha = "";
     while (br.ready())
     {
         vLinha = br.readLine();
         if(vLinha == null) { break; }                              
         bw.write(vLinha System.lineSeparator());                 
         if (lLinhas % lLimiteLinhas == 0L && lLinhas > 0L)
         {                   
             bw.flush();
             bw.close();                     
               lPart;
             sNomeArquivoDestino = sPathDestino "\\" sFileName.replace(".TXT", "") "-Part-"  String.format("d" ,lPart) ".TXT";
             fw = new FileWriter(sNomeArquivoDestino);    // Compile error: The resource fw of a try-with-resources statement cannot be assigned         
             bw = new BufferedWriter(fw);    // Compile error: The resource bw of a try-with-resources statement cannot be assigned         
         }                                  
           lLinhas; 
     }             
 }
 catch (Exception ex)
 {           
     throw ex;
 }

CodePudding user response：

As the BufferedWriter is used to write several numbered partial files, one does not have an automatically closing file for a try-with-resources syntax.

Easiest is to have a finally block and do all oneself. Of course one could also introduce a second nested loop with try-with-resources for the output of a part.

First I would use Files, Path, and Paths for a shorter usage of otherwise nested file constructors. Also the text encoding of the computer is the default one. Better make it explicit. (Best would have been StandardCharsets.UTF_8 for full Unicode power, when possible.)

Using ready() is wrong, as it is a test, whether a read will block (the current buffer is empty). Here the right thing to do is to request a read. Otherwise you might be so fast, still nothing is there, and though there is still something on disk, you stop reading.

One might use sNomeArquivoDestino = String.format("...%s ...", ..., ...); for a nicer style.

    Charset charset = Charset.defaultCharset();
    Path arguivo = Paths.get(sArguivo);
    BufferedWriter bw = null;
    try (BufferedReader br = Files.newBufferedReader(arguivo, charset)) {
        long lPart = 0;
        long lLinhas = 0L;
        for (;;) {
            String vLinha = br.readLine();
            if (vLinha == null) {
                break;
            }
            if (lLinhas % lLimiteLinhas == 0L) {
                if (bw != null) {
                    bw.close();
                    bw = null;
                }
                sNomeArquivoDestino = sPathDestino   "\\"
                      sFileName.replace(".TXT", "")   "-Part-"
                      String.format("d", lPart)   ".TXT";
                Path arquivoDestino = Paths.get(sNomeArquivoDestino);
                bw = Files.newBufferedWriter(arquivoDestino, charset);
                  lPart;
            }
            bw.write(vLinha);
            bw.write(System.lineSeparator());
              lLinhas;
        }
    } finally {
        if (bw != null) {
            bw.close();
        }
    }

By the way, Hungarian notation with prefixes like s and l are not common in java, in favor of more fluent names. (Compare old MS C with Linux C .)

CodePudding user response：

You'll need to change your logic to use try-with-resources inside try-with-resources. In pseudo code:

try (fis; br):
    for each partition in br:
        try (fw; bw):
            write partition to bw

Assuming that you should always write at least one partition, this could be done changed a bit:

try (fis; br):
    while (true):
        try (fw; bw):
            write partition
            - continue when the partition is full
            - break when no more data