guava I/O Handling existing InputStreams and OutputStreams

Example

Reading the content of an InputStream as a byte array:

// Reading from a file
try (InputStream in = new FileInputStream("in.dat")) {
  byte[] content = ByteStreams.toByteArray(in);
  // do something with content
}

Copying an InputStream to an OutputStream:

// Copying the content from a file in.dat to out.dat.
try (InputStream in = new FileInputStream("in.dat");
     OutputStream out = new FileOutputStream("out.dat")) {
  ByteStreams.copy(in, out);
}

Note: to copy files directly, it's better to use Files.copy(sourceFile, destinationFile).

Reading an entire predefined byte array from an InputStream:

try (InputStream in = new FileInputStream("in.dat")) {
  byte[] bytes = new byte[16];
  ByteStreams.readFully(in, bytes);
  // bytes is totally filled with 16 bytes from the InputStream.
} catch (EOFException ex) {
  // there was less than 16 bytes in the InputStream.
}

Skipping n bytes from the InputStream:

try (InputStream in = new FileInputStream("in.dat")) {
  ByteStreams.skipFully(in, 20);
  // the next byte read will be the 21st.
  int data = in.read();
} catch (EOFException e) {
  // There was less than 20 bytes in the InputStream.
}

Creating an OutputStream that discards everything that is written to it:

try (InputStream in = new FileInputStream("in.dat");
     OutputStream out = ByteStreams.nullOutputStream()) {
  ByteStreams.copy(in, out);
  // The whole content of in is read into... nothing.
}