Buffers & Writers (Readers)

2. To not overload the underlying system/OS, it is recommended to use Buffer:

BufferedOutputStream bos = new BufferedOutputStream(fos);
...
bos.write(data);
bos.close();

3. Next, Writers, and Readers, are used to manipulate text rather than bytes:

Writer writer = new OutputStreamWriter(bos);
writer.write("abc");
writer.close();

Nb. The preceding elements can be simplified by using FileWriter.

try {
  FileWriter f = new FileWriter("output.csv");
  f.write("abc");
  f.close();    
} catch (Exception e) {
  e.printStackTrace();
}