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 the 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.read()); // 10
    System.out.println(is.read()); // 20
    System.out.println(is.read()); // 30
    System.out.println(is.read()); // -1
}

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.

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
}

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.

• InputStream with Examples