FileOutputStream wait for finishing writing

Question

I have many byte[] pieces to write to a file and these pieces are kinda big and I think the bytes are getting mixed...

Is there any methods to wait for .write(byte[]) to finish his work or other ways to deal with this problem? When I watch the file the first half is ok , then when I start writing the second half, some time it ends with the first half.... The byte array is good, I tested them. If you need any explain of code feel free ask.

try (FileOutputStream fos = new FileOutputStream(Main.newFile)) {
        for (int y = 0; y < piecesCount; y++) {
            if (this.myList[y] == 1) {
                fos.write(this.piecesArray.get(y).piece);
                fos.flush();
                System.out.println("Im writing " + y + " piece");
            } else {
                y--;
            }
        }
        fos.close();
    } catch (FileNotFoundException ex) {
    } catch (IOException | InterruptedException ex) {
    }

Answer 1

Well, if piecesCount is a long the int y variable may overflow and start wrtiting the first part of the array.

If this is not the case, I don't see other bugs in this code that may cause what you described. In which case there must be something going on in

piecesArray.get(y).piece