文字读写不完整？

Question

There seems to be a problem with reading and writing from a textfile.

While having two different files I printed out the content and it doesn't seem the same as it should be in the textfiles.

I tried to add + and without, and to add bw.close() or without. I tried also to use scanner instead, but it didn't print out anything.

Could it be changed somehow ?

  private void readFromFile(File cf2) throws IOException, Exception {

   FileReader fr = new FileReader(cf2);
   try (BufferedReader bw = new BufferedReader(fr)) {
    System.out.println("Wait while reading !");

    while(bw.readLine() != null)
    s1 += bw.readLine();
    System.out.println(s1);
    bw.close();
   } System.out.println("File read !");
  }

Answer 1

You are using bw.readLine() twice, witch consumes two lines, but you are adding only one of them to s1 each time. Try

String line;
while((line = bw.readLine()) != null)
    s1 += line;
System.out.println(s1);

Answer 2

Half of your readLine calls are used for checking the data for null , the other half get added to s1 . That's why you get only part of the input.

To fix your code, make a loop like this:

while (true) {
    String s = bw.readLine();
    if (s == null) break;
    s1 += s;
}

However, this is grossly inefficient. You would be better off using StringBuffer :

StringBuffer sb = new StringBuffer()
while (true) {
    String s = bw.readLine();
    if (s == null) break;
    sb.append(s);
    // Uncomment the next line to add separators between lines
    // sb.append('\n');
}
s1 = sb.toString();

Note that none of '\\n' symbols from your file would be in the output string. To add separators back, uncomment the commented line in the code above.

Answer 3

You call readline() twice, so you only get every second line.

  private void readFromFile(File cf2) throws IOException, Exception {

   FileReader fr = new FileReader(cf2);
   try (BufferedReader br = new BufferedReader(fr)) {
       System.out.println("Wait while reading !");
       StringBuilder sb = new StringBuilder();
       String s;
       while((s = br.readLine()) != null) {
           sb.append(s);
       }
       System.out.println(sb.toString());
   }
  System.out.println("File read !");
  }

You don't need to close br because that is done by try-with-resources.