"IndexOutOfBoundException" not seeing where exactly

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The file I used for testing created a byte[] of length 47, and the last index accessed through the "fos1.write(buffer,midle,(buffer.length - 1))" (exception thrown at line 16) is 46. I don't see where the error is coming from. Thanks!(code below)

public static void main(String[] args) {
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      try(FileInputStream fis = new FileInputStream(br.readLine());
          FileOutputStream fos0 = new FileOutputStream(br.readLine());
          FileOutputStream fos1 = new FileOutputStream(br.readLine())){

          if(fis.available() > 0){
              final int length = fis.available();
              byte[] buffer = new byte[length];
              fis.read(buffer);

              int midle = 0 ;
              if((buffer.length % 2) != 0){
                  midle = (buffer.length / 2);
                  fos0.write(buffer, 0,midle);
                  fos1.write(buffer,midle + 1,(buffer.length - 1));
              }else {
                  midle = buffer.length / 2;
                  fos0.write(buffer,0,midle - 1);
                  fos1.write(buffer,midle + 1, buffer.length - 1);
              }

          }

      }catch (IOException ioe){

      }
  }

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Guadalupe Gagnon

Level 37 , Tampa, United States

9 March 2020, 19:05

line 16 isn't going to print the correct values. Lets say you have a string: "0123456789" and the variable middle = 5. Line 15 would split that string into: "01234" and line 16 would split it into: "678" The same problems would occur with lines 19 and 20 with the added effect that you are truncating more from the first line. Also, if you had a string such as "01", middle would be 1 and line 16/20 would try to start at index 2. This is where the IndexOutOfBoundsException is being thrown. Hint: you don't need to check if the length is even or odd.

catalinene

Level 29 , Greven, Germany

9 March 2020, 21:23

So I modified the code and now it looks like this (posted below) but it throws the same exception. My logic (if I undestood corectly) is the following: if I have the elements within the buffer array :"0123456789" length = 10, midle = 5. So the method fis0.write(buffer, 0 , midle): writes "01234" and fis1.write(buffer, midle , buffer.length): writes "56789". Where am I wrong?

if(fis.available() > 0){
                byte[] buffer = new byte[fis.available()];
                fis.read(buffer);

                int midle = (buffer.length / 2);
                fos0.write(buffer, 0,midle);
                fos1.write(buffer,midle,buffer.length);
            }

Guadalupe Gagnon

Level 37 , Tampa, United States

9 March 2020, 21:40

solution

try this:

fos1.write(Arrays.copyOfRange(buffer,midle,buffer.length));

Your code looked good to me but line 7 doesn't seem to work. I don't know why, ill have to research this when i have time.

catalinene

Level 29 , Greven, Germany

9 March 2020, 22:10

After adding this:

fos1.write(Arrays.copyOfRange(buffer,midle,buffer.length));

And another small change to how the "midle" is calculated (see code below) it passed. Thanks a lot for your feedback! If you remove Arrays.copyOfRange(), the error does return. Would be great if you find the time, I'm super curious why.

if(fis.available() > 0){
                byte[] buffer = new byte[fis.available()];
                fis.read(buffer);

                int midle = (buffer.length / 2) + (buffer.length % 2 == 0 ? 0:1);
                fos0.write(buffer, 0,midle);
                fos1.write(Arrays.copyOfRange(buffer,midle,buffer.length));

            }

Guadalupe Gagnon

Level 37 , Tampa, United States

11 March 2020, 13:34

So the problem was that an IndexOutOfBounds exception was occurring on this line:

fos1.write(buffer,midle,buffer.length);

It took me removing the try-catch block to figure that much out. The way that the write method works is that the three arguments are: (dataInBytes, startPoint, AmountOfBytesFromStartPoint) The way the third argument was being used in the original line of code was as an end point. It would work like this:

fos1.write(buffer, midle, buffer.length - midle);

catalinene

Level 29 , Greven, Germany

11 March 2020, 15:10

Okay so the 3rd argument is not an Endpoint but the total amount of bytes left from the start point. You're amazing, thanks a lot!

Guadalupe Gagnon

Level 37 , Tampa, United States

11 March 2020, 15:18

Exactly, and thanks, I learn a lot from helping people. It is strange that the Arrays.copyOfRange() method and the write() method are structured similarly but have different 3rd arguments. Java, as well as most programming languages, is typically structured with consistency in mind. Anyways, happy coding. Feel free to ask questions if you are stuck on anything.

catalinene

Level 29 , Greven, Germany

11 March 2020, 19:29

Was very strange indeed! Guess we have to get used of seeing some chaos here and there haha! Thanks, you as well!