CODEWITHSUNDEEP
java
Stanley Mungai
Stanley Mungai

Reputation: 4150

Skipping certain parts of a textfile while reading in java

I have a text file that I am reading. It has chunks that I would want to remove. Is there a way I can say If the reader comes across a String "STATEMENT OF ACCOUNT" it skips reading the 10 lines before that Statement. This is the code I am currently using which is reading everything from the Text file.

  for(int i = 0; i < filenames.length; i++){
   FileInputStream fstemp = new FileInputStream("C:/Temporary/" + filenames[i]); 
   FileOutputStream fos = new FileOutputStream("C:/Statements/" + filenames[i]);  
   DataInputStream in1 = new DataInputStream(fstemp);
   UniqueLineReader brtemp = new UniqueLineReader(new InputStreamReader(in1));
   BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(fos));
   String strLine;
   while((strLine = brtemp.readLine()) != null){
     bw.write(strLine);
     bw.newLine();
     bw.flush();

   }


    }

Upvotes: 0

Views: 389

Answers (3)

Mike Partridge
Mike Partridge

Reputation: 5281

It sounds like you need to maintain a buffer of 10 lines so that when you encounter your special line, you can abandon the contents. Until you see it, you add every line to one end and only output from the other end when the buffer is full. The answers to this question recommend a Queue or CircularFifoBuffer for this type of situation.

Here's an untested code sample using a CircularFifoBuffer:

for (int i = 0; i < filenames.length; i++) {
    FileInputStream fstemp = new FileInputStream("C:/Temporary/" + filenames[i]);
    FileOutputStream fos = new FileOutputStream("C:/Statements/" + filenames[i]);
    DataInputStream in1 = new DataInputStream(fstemp);
    UniqueLineReader brtemp = new UniqueLineReader(new InputStreamReader(in1));
    BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(fos));
    Buffer ringbuf = new CircularFifoBuffer(10);
    String strLine;
    while ((strLine = brtemp.readLine()) != null) {
        if (strLine.equals("STATEMENT OF ACCOUNT")) {
            ringbuf.clear();
        }

        ringbuf.add(strLine);

        if (ringbuf.isFull()) {
            bw.write(ringbuf.remove());
            bw.newLine();
            bw.flush();
        }
    }

    for (Object item : ringbuf) {
        bw.write(item);
        bw.newLine();
        bw.flush();
    }
}

Upvotes: 1

Sean Reilly
Sean Reilly

Reputation: 21836

You can do it by buffering the preceding 10 lines in a queue:

Queue<String> queue = new LinkedList<String>();
String strLine;
while ((strLine = brtemp.readLine()) != null {
    queue.add(strLine);
    if (strLine.equals("STATEMENT OF ACCOUNT")) {
        queue.clear();
        continue;
    }

    while (queue.size() >= 10) {
        bw.write(queue.remove());
        bw.newLine();
    }
}
while (!queue.isEmpty()) {
    bw.write(queue.remove());
    bw.newLine();
}
bw.flush();

Upvotes: 1

Jon Skeet
Jon Skeet

Reputation: 1500525

I'm assuming you actually want to skip the 10 lines after the "STATEMENT OF ACCOUNT" line. In which case, you want something like this:

int linesToSkip = 0;
String strLine;
while((strLine = brtemp.readLine()) != null) {
  if (linesToSkip > 0) {
    linesToSkip--;
    continue;
  }
  if (strLine.equals("STATEMENT OF ACCOUNT")) {
    linesToSkip = 10;
    continue;
  }
  bw.write(strLine);
  bw.newLine();
  bw.flush();
}

If you really want to somehow obliterate the previous ten lines, then you'd need to delay output (e.g. saving it in a cyclical buffer) until ten lines later, just in case you see "STATEMENT OF ACCOUNT" in a few lines' time.

Upvotes: 4

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