Java : OutputStream with Examples

final var file = Path.of("R:", "java-work", "test.data");
System.out.println(file); // R:\java-work\test.data

try (final var os = Files.newOutputStream(file)) {
    os.write(10);
    os.write(20);
    os.write(30);
}

final var bytes = Files.readAllBytes(file);
System.out.println(Arrays.toString(bytes)); // [10, 20, 30]

OutputStream ()

Constructor for subclasses to call.

I think it's rare to create a subclass of OutputStream. Therefore, the code example is omitted.

void close ()

Closes this output stream and releases any system resources associated with this stream.

final var file = Path.of("R:", "java-work", "test.data");
System.out.println(file); // R:\java-work\test.data

try (final var os = Files.newOutputStream(file)) {
    os.write(123);
}

final var bytes = Files.readAllBytes(file);
System.out.println(Arrays.toString(bytes)); // [123]

// An example without a try-with-resources statement.
final var file = Path.of("R:", "java-work", "test.data");
System.out.println(file); // R:\java-work\test.data

final var os = Files.newOutputStream(file);
try {
    os.write(123);
} finally {
    os.close();
}

final var bytes = Files.readAllBytes(file);
System.out.println(Arrays.toString(bytes)); // [123]

void flush ()

Flushes this output stream and forces any buffered output bytes to be written out.

final var file = Path.of("R:", "java-work", "test.data");
System.out.println(file); // R:\java-work\test.data

try (final OutputStream os = new BufferedOutputStream(Files.newOutputStream(file))) {

    os.write(123);
    System.out.println(Arrays.toString(Files.readAllBytes(file))); // []

    os.flush();
    System.out.println(Arrays.toString(Files.readAllBytes(file))); // [123]
}

static OutputStream nullOutputStream ()

Returns a new OutputStream which discards all bytes.

final byte[] b = {1, 2, 3};
final var os = OutputStream.nullOutputStream();

os.write(123);
os.write(b);
os.write(b, 0, 2);
os.flush();

os.close();

//os.write(123); // IOException: Stream closed

void write (byte[] b)

Writes b.length bytes from the specified byte array to this output stream.

final var file = Path.of("R:", "java-work", "test.data");
System.out.println(file); // R:\java-work\test.data

try (final var os = Files.newOutputStream(file)) {

    os.write(new byte[]{10, 20});

    final var bytes1 = Files.readAllBytes(file);
    System.out.println(Arrays.toString(bytes1)); // [10, 20]

    os.write(new byte[]{30, 40, 50});

    final var bytes2 = Files.readAllBytes(file);
    System.out.println(Arrays.toString(bytes2)); // [10, 20, 30, 40, 50]
}

void write (byte[] b, int off, int len)

Writes len bytes from the specified byte array starting at offset off to this output stream.

final var file = Path.of("R:", "java-work", "test.data");
System.out.println(file); // R:\java-work\test.data

final byte[] b = {10, 20, 30, 40, 50};

try (final var os = Files.newOutputStream(file)) {

    os.write(b, 0, 2);

    final var bytes1 = Files.readAllBytes(file);
    System.out.println(Arrays.toString(bytes1)); // [10, 20]

    os.write(b, 2, 3);

    final var bytes2 = Files.readAllBytes(file);
    System.out.println(Arrays.toString(bytes2)); // [10, 20, 30, 40, 50]
}

abstract void write (int b)

Writes the specified byte to this output stream.

The byte to be written is the eight low-order bits of the argument b.

final var file = Path.of("R:", "java-work", "test.data");
System.out.println(file); // R:\java-work\test.data

try (final var os = Files.newOutputStream(file)) {

    os.write(1);

    final var bytes1 = Files.readAllBytes(file);
    System.out.println(Arrays.toString(bytes1)); // [1]

    os.write(127);

    final var bytes2 = Files.readAllBytes(file);
    System.out.println(Arrays.toString(bytes2)); // [1, 127]

    os.write(128);

    final var bytes3 = Files.readAllBytes(file);
    System.out.println(Arrays.toString(bytes3)); // [1, 127, -128]

    os.write(129);

    final var bytes4 = Files.readAllBytes(file);
    System.out.println(Arrays.toString(bytes4)); // [1, 127, -128, -127]

    os.write(255);

    final var bytes5 = Files.readAllBytes(file);
    System.out.println(Arrays.toString(bytes5)); // [1, 127, -128, -127, -1]

    os.write(256);

    final var bytes6 = Files.readAllBytes(file);
    System.out.println(Arrays.toString(bytes6)); // [1, 127, -128, -127, -1, 0]

    os.write(257);

    final var bytes7 = Files.readAllBytes(file);
    System.out.println(Arrays.toString(bytes7)); //[1, 127, -128, -127, -1, 0, 1]
}