Adding buffer when writing byte[] to OutputStream

Question

In my method, I'm saving data from file to an output stream.

For now, it looks like this

public void readFileToOutputStream(Path path, OutputStream os) {
    byte[] barr = Files.readAllBytes(path)

    os.write(barr);
    os.flush();
}

But in this solution, all bytes are loaded into memory, and I want to use buffer to release some of it.

What can I use to supply my reading with buffer?

Take a look at this answer in the linked question:http://stackoverflow.com/a/19194580/1743880 There is a built-in for that: `Files.copy(Path, OutputStream)`. — Tunaki, May 24 '16 at 17:00

score 1 · Accepted Answer · answered May 24 '16 at 09:54

easist way is to use Commons IO library

public void readFileToOutputStream(Path path, OutputStream os) throws IOException {
  try(InputStream in = new FileInputStream(path.toFile())){
    IOUtils.copy(in, os);
  }
}

You can implement on your own similar to IOUtils.copy

public void readFileToOutputStream(Path path, OutputStream os) throws IOException {
  try (InputStream fis = new FileInputStream(path.toFile());
       InputStream bis = new BufferedInputStream(fis)) {
    byte[] buffer = new byte[4096];
    int n;
    while ((n = bis.read(buffer)) >= 0) {
      os.write(buffer, 0, n);
    }
  }
}

score 0 · Answer 2 · answered May 24 '16 at 08:38

If i understand your question right, you would like to only write a specified amount of bytes to memory?

outputstreams write method can also write a specified byte array from a starting offset and length.

https://docs.oracle.com/javase/7/docs/api/java/io/OutputStream.html

public void readFileToOutputStream(Path path, OutputStream os, int off, int len) {
    byte[] barr = Files.readAllBytes(path)

    os.write(barr, off, len);
    os.flush();
}

score 0 · Answer 3 · answered May 24 '16 at 08:41

Use buffered streams to manage the buffer for you:

public void readFileToOutputStream(Path path, OutputStream os) {
    try (FileInputStream fis = new FileInputStream(path.toFile())) {
        try (BufferedInputStream bis = new BufferedInputStream(fis)) {
            try (DataInputStream dis = new DataInputStream(bis)) {
                try (BufferedOutputStream bos = new BufferedOutputStream(os)) {
                    try (DataOutputStream dos = new DataOutputStream(bos)) {
                        try {
                            while (true) {
                                dos.writeByte(dis.readByte());
                            }
                        } catch (EOFException e) {
                            // normal behaviour
                        }
                    }
                }
            }
        }
    }
}

You can have multiple resources inside the `try` part instead of nesting as many try blocks as resources. — Tunaki, May 24 '16 at 16:57

score 0 · Answer 4 · answered May 24 '16 at 09:09

0

Use FileInputStream::read(byte[] b, int off, int len) link to read up to len bytes to buffer b and FileOutputStream::write(byte[] b, int off, int len) link2 to write from buffer

answered May 24 '16 at 09:09

Sergei Rybalkin

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Adding buffer when writing byte[] to OutputStream

4 Answers4