guava I/O Sources and sinks

Example

Sources and sinks are objects that know how to open streams.

	Bytes	Chars
Reading	ByteSource	CharSource
Writing	ByteSink	CharSink

Creating sources and sinks

Note: for all examples, consider UTF_8 as if the following import is set:

import static java.nio.charset.StandardCharsets.UTF_8;

Reading from a file

ByteSource dataSource = Files.asByteSource(new File("input.dat"));
CharSource textSource = Files.asCharSource(new File("input.txt"), UTF_8);

Writing to a file

ByteSink dataSink = Files.asByteSink(new File("output.dat"));
CharSink textSink = Files.asCharSink(new File("output.txt"), UTF_8);

Reading from a URL

ByteSource dataSource = Resources.asByteSource(url);
CharSource textSource = Resources.asCharSource(url, UTF_8);

Reading from in memory data

ByteSource dataSource = ByteSource.wrap(new byte[] {1, 2, 3});
CharSource textSource = CharSource.wrap("abc");

Converting from bytes to chars

ByteSource originalSource = ...
CharSource textSource = originalSource.asCharSource(UTF_8);

Converting from chars to bytes

(From Guava 20 onwards)

CharSource originalSource = ...
ByteSource dataSource = originalSource.asByteSource(UTF_8);

Using sources and sinks

Common operations

Opening a stream

InputStream inputStream = byteSource.openStream();
OutputStream outputStream = byteSink.openStream();
Reader reader = charSource.openStream();
Writer writer = charSink.openStream();

Opening a buffered stream

InputStream bufferedInputStream = byteSource.openBufferedStream();
OutputStream bufferedOutputStream = byteSink.openBufferedStream();
BufferedReader bufferedReader = charSource.openBufferedStream();
Writer bufferedWriter = charSink.openBufferedStream();

Source operations

Reading from a source:

ByteSource source = ...
byte[] bytes = source.read();

CharSource source = ...
String text = source.read();

Reading lines from a source:

CharSource source = ...
ImmutableList<String> lines = source.readLines();

Reading the first line from a source:

CharSource source = ...
String firstLine = source.readFirstLine();

Copying from a source to a sink:

ByteSource source = ...
ByteSink sink = ...
source.copyTo(sink);

CharSource source = ...
CharSink sink = ...
source.copyTo(sink);

Typical usage

CharSource source = ...
try (Reader reader = source.openStream()) {
  // use the reader
}