Java : FilterOutputStream with Examples

class MyOutputStream extends FilterOutputStream {
    MyOutputStream(OutputStream out) {
        super(out);
    }
}

final var out = new ByteArrayOutputStream();

try (final var os = new MyOutputStream(out)) {
    os.write(10);
    os.write(20);
    os.write(30);
}

System.out.println(Arrays.toString(out.toByteArray())); // [10, 20, 30]

protected OutputStream out

The underlying output stream to be filtered.

class MyOutputStream extends FilterOutputStream {
    MyOutputStream(OutputStream out) {
        super(out);
    }

    OutputStream getOut() {
        return out;
    }
}

final var out = new ByteArrayOutputStream();

try (final var os = new MyOutputStream(out)) {
    System.out.println(os.getOut() == out); // true
}

FilterOutputStream (OutputStream out)

Creates an output stream filter built on top of the specified underlying output stream.

class MyOutputStream extends FilterOutputStream {
    MyOutputStream(OutputStream out) {
        super(out);
    }
}

final var out = new ByteArrayOutputStream();

try (final var os = new MyOutputStream(out)) {
    os.write(10);
    os.write(20);
    os.write(30);
}

System.out.println(Arrays.toString(out.toByteArray())); // [10, 20, 30]

void close ()

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

final var out = new ByteArrayOutputStream();

try (final FilterOutputStream os = new BufferedOutputStream(out)) {
    os.write(10);
    os.write(20);
    os.write(30);
}

System.out.println(Arrays.toString(out.toByteArray())); // [10, 20, 30]

// An example without a try-with-resources statement.
final var out = new ByteArrayOutputStream();
final FilterOutputStream os = new BufferedOutputStream(out);
try {
    os.write(10);
    os.write(20);
    os.write(30);
} finally {
    os.close();
}

System.out.println(Arrays.toString(out.toByteArray())); // [10, 20, 30]

void flush ()

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

final var out = new ByteArrayOutputStream();

try (final FilterOutputStream os = new BufferedOutputStream(out)) {

    os.write(10);
    System.out.println(Arrays.toString(out.toByteArray())); // []

    os.flush();
    System.out.println(Arrays.toString(out.toByteArray())); // [10]

    os.write(20);
    System.out.println(Arrays.toString(out.toByteArray())); // [10]

    os.flush();
    System.out.println(Arrays.toString(out.toByteArray())); // [10, 20]

    os.write(30);
    System.out.println(Arrays.toString(out.toByteArray())); // [10, 20]
}

System.out.println(Arrays.toString(out.toByteArray())); // [10, 20, 30]

void write (byte[] b)

Writes b.length bytes to this output stream.

final var out = new ByteArrayOutputStream();

try (final FilterOutputStream os = new BufferedOutputStream(out)) {

    final byte[] b1 = {10, 20};

    os.write(b1);
    os.flush();
    System.out.println(Arrays.toString(out.toByteArray())); // [10, 20]

    final byte[] b2 = {30, 40, 50};

    os.write(b2);
    os.flush();
    System.out.println(Arrays.toString(out.toByteArray())); // [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 out = new ByteArrayOutputStream();

try (final FilterOutputStream os = new BufferedOutputStream(out)) {

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

    os.write(b, 0, 2);
    os.flush();
    System.out.println(Arrays.toString(out.toByteArray())); // [10, 20]

    os.write(b, 2, 3);
    os.flush();
    System.out.println(Arrays.toString(out.toByteArray())); // [10, 20, 30, 40, 50]
}

void write (int b)

Writes the specified byte to this output stream.

Please see FilterOutputStream(OutputStream out).

nullOutputStream

Please see the link below.

• Java API Examples : OutputStream