Java : FilterInputStream with Examples

class MyInputStream extends FilterInputStream {
    MyInputStream(InputStream in) {
        super(in);
    }
}

final byte[] buf = {10, 20, 30};

try (final var is = new MyInputStream(new ByteArrayInputStream(buf))) {
    System.out.println(is.read()); // 10
    System.out.println(is.read()); // 20
    System.out.println(is.read()); // 30
    System.out.println(is.read()); // -1
}

protected InputStream in

The input stream to be filtered.

class MyInputStream extends FilterInputStream {
    MyInputStream(InputStream in) {
        super(in);
    }

    InputStream getIn() {
        return in;
    }
}

final var byteArrayInputStream = new ByteArrayInputStream(new byte[0]);

try (final var is = new MyInputStream(byteArrayInputStream)) {
    System.out.println(is.getIn() == byteArrayInputStream); // true
}

FilterInputStream (InputStream in)

Creates a FilterInputStream by assigning the argument in to the field this.in so as to remember it for later use.

class MyInputStream extends FilterInputStream {
    MyInputStream(InputStream in) {
        super(in);
    }
}

final byte[] buf = {10, 20, 30};
try (final var is = new MyInputStream(new ByteArrayInputStream(buf))) {
    System.out.println(is.read()); // 10
    System.out.println(is.read()); // 20
    System.out.println(is.read()); // 30
    System.out.println(is.read()); // -1
}

int available ()

Returns an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking by the next caller of a method for this input stream.

class MyInputStream extends FilterInputStream {
    MyInputStream(InputStream in) {
        super(in);
    }
}

final byte[] buf = {10, 20, 30};
try (final var is = new MyInputStream(new ByteArrayInputStream(buf))) {
    System.out.println(is.available()); // 3
    System.out.println(is.read()); // 10

    System.out.println(is.available()); // 2
    System.out.println(is.read()); // 20

    System.out.println(is.available()); // 1
    System.out.println(is.read()); // 30

    System.out.println(is.available()); // 0
    System.out.println(is.read()); // -1
}

void close ()

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

final byte[] buf = {10, 20, 30};
try (final FilterInputStream is = new BufferedInputStream(
        new ByteArrayInputStream(buf))) {
    final var ret = is.readAllBytes();
    System.out.println(Arrays.toString(ret)); // [10, 20, 30]
}

// An example without a try-with-resources statement.
final byte[] buf = {10, 20, 30};
final FilterInputStream is = new BufferedInputStream(new ByteArrayInputStream(buf));
try {
    final var ret = is.readAllBytes();
    System.out.println(Arrays.toString(ret)); // [10, 20, 30]
} finally {
    is.close();
}

void mark (int readlimit)

Marks the current position in this input stream.

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

try (final FilterInputStream is = new BufferedInputStream(
        new ByteArrayInputStream(buf))) {
    System.out.println(is.read()); // 10
    System.out.println(is.read()); // 20

    is.mark(4);

    System.out.println(is.read()); // 30
    System.out.println(is.read()); // 40
    System.out.println(is.read()); // 50
    System.out.println(is.read()); // -1

    is.reset();

    System.out.println(is.read()); // 30
    System.out.println(is.read()); // 40
    System.out.println(is.read()); // 50
    System.out.println(is.read()); // -1
}

boolean markSupported ()

Tests if this input stream supports the mark and reset methods.

class MyInputStream extends FilterInputStream {
    MyInputStream(InputStream in) {
        super(in);
    }
}

final byte[] buf = {10, 20, 30};

try (final var is = new MyInputStream(new ByteArrayInputStream(buf))) {
    System.out.println(is.markSupported()); // true
}

int read ()

Reads the next byte of data from this input stream.

Please see FilterInputStream(InputStream in).

int read (byte[] b)

Reads up to b.length bytes of data from this input stream into an array of bytes.

class MyInputStream extends FilterInputStream {
    MyInputStream(InputStream in) {
        super(in);
    }
}

final byte[] bytes = {10, 20, 30, 40, 50};
try (final var is = new MyInputStream(new ByteArrayInputStream(bytes))) {
    final var b1 = new byte[3];

    System.out.println(is.read(b1)); // 3
    System.out.println(Arrays.toString(b1)); // [10, 20, 30]

    final var b2 = new byte[3];

    System.out.println(is.read(b2)); // 2
    System.out.println(Arrays.toString(b2)); // [40, 50, 0]

    final var b3 = new byte[3];

    System.out.println(is.read(b3)); // -1
    System.out.println(Arrays.toString(b3)); // [0, 0, 0]
}

int read (byte[] b, int off, int len)

Reads up to len bytes of data from this input stream into an array of bytes.

class MyInputStream extends FilterInputStream {
    MyInputStream(InputStream in) {
        super(in);
    }
}

final byte[] buf = {10, 20, 30};

try (final var is = new MyInputStream(new ByteArrayInputStream(buf))) {
    final var b1 = new byte[3];

    System.out.println(is.read(b1, 0, 1)); // 1
    System.out.println(Arrays.toString(b1)); // [10, 0, 0]

    final var b2 = new byte[3];

    System.out.println(is.read(b2, 0, 2)); // 2
    System.out.println(Arrays.toString(b2)); // [20, 30, 0]

    final var b3 = new byte[3];

    System.out.println(is.read(b3, 0, 3)); // -1
    System.out.println(Arrays.toString(b3)); // [0, 0, 0]
}

try (final var is = new MyInputStream(new ByteArrayInputStream(buf))) {
    final var b1 = new byte[3];

    System.out.println(is.read(b1, 2, 1)); // 1
    System.out.println(Arrays.toString(b1)); // [0, 0, 10]

    final var b2 = new byte[3];

    System.out.println(is.read(b2, 1, 2)); // 2
    System.out.println(Arrays.toString(b2)); // [0, 20, 30]

    final var b3 = new byte[3];

    System.out.println(is.read(b3, 0, 3)); // -1
    System.out.println(Arrays.toString(b3)); // [0, 0, 0]
}

void reset ()

Repositions this stream to the position at the time the mark method was last called on this input stream.

Please see mark(int readlimit).

long skip (long n)

Skips over and discards n bytes of data from the input stream.

class MyInputStream extends FilterInputStream {
    MyInputStream(InputStream in) {
        super(in);
    }
}

final byte[] buf = {10, 20, 30, 40, 50, 60, 70, 80, 90, 100};

try (final var is = new MyInputStream(new ByteArrayInputStream(buf))) {
    System.out.println(is.read()); // 10

    System.out.println(is.skip(1)); // 1
    System.out.println(is.read()); // 30

    System.out.println(is.skip(2)); // 2
    System.out.println(is.read()); // 60

    System.out.println(is.skip(3)); // 3
    System.out.println(is.read()); // 100

    System.out.println(is.skip(1)); // 0
    System.out.println(is.read()); // -1
}

nullInputStream, readAllBytes, readNBytes, readNBytes, skipNBytes, transferTo

Please see the link below.

• Java API Examples : InputStream