Module java.base
Package java.io

Class FilterInputStream

java.lang.Object
java.io.InputStream
java.io.FilterInputStream
All Implemented Interfaces:
Closeable, AutoCloseable
Direct Known Subclasses:
BufferedInputStream, CheckedInputStream, CipherInputStream, DataInputStream, DeflaterInputStream, DigestInputStream, InflaterInputStream, LineNumberInputStream, ProgressMonitorInputStream, PushbackInputStream
public class FilterInputStream extends InputStream
A FilterInputStream contains some other input stream, which it uses as its basic source of data, possibly transforming the data along the way or providing additional functionality. The class FilterInputStream itself simply overrides all methods of InputStream with versions that pass all requests to the contained input stream. Subclasses of FilterInputStream may further override some of these methods and may also provide additional methods and fields.
Since:
1.0

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    protected InputStream
    in
    The input stream to be filtered.

  • Constructor Summary

    Constructors
    Modifier
    Constructor
    Description
    protected
    FilterInputStream​(InputStream in)
    Creates a FilterInputStream by assigning the argument in to the field this.in so as to remember it for later use.

  • Method Summary

    Modifier and Type
    Method
    Description
    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.
    void
    close()
    Closes this input stream and releases any system resources associated with the stream.
    void
    mark​(int readlimit)
    Marks the current position in this input stream.
    boolean
    markSupported()
    Tests if this input stream supports the mark and reset methods.
    int
    read()
    Reads the next byte of data from this input stream.
    int
    read​(byte[] b)
    Reads up to b.length bytes of data from this input stream into an array of bytes.
    int
    read​(byte[] b, int off, int len)
    Reads up to len bytes of data from this input stream into an array of bytes.
    void
    reset()
    Repositions this stream to the position at the time the mark method was last called on this input stream.
    long
    skip​(long n)
    Skips over and discards n bytes of data from the input stream.

    Methods declared in class java.io.InputStream

    nullInputStream, readAllBytes, readNBytes, readNBytes, skipNBytes, transferTo

    Methods declared in class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

    • in

      protected volatile InputStream in
      The input stream to be filtered.

  • Constructor Details

    • FilterInputStream

      protected FilterInputStream​(InputStream in)
      Creates a FilterInputStream by assigning the argument in to the field this.in so as to remember it for later use.
      Parameters:
      in - the underlying input stream, or null if this instance is to be created without an underlying stream.

  • Method Details

    • read

      public int read() throws IOException
      Reads the next byte of data from this input stream. The value byte is returned as an int in the range 0 to 255. If no byte is available because the end of the stream has been reached, the value -1 is returned. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown.

      This method simply performs in.read() and returns the result.

      Specified by:
      read in class InputStream
      Returns:
      the next byte of data, or -1 if the end of the stream is reached.
      Throws:
      IOException - if an I/O error occurs.
      See Also:
      in

    • read

      public int read​(byte[] b) throws IOException
      Reads up to b.length bytes of data from this input stream into an array of bytes. This method blocks until some input is available.

      This method simply performs the call read(b, 0, b.length) and returns the result. It is important that it does not do in.read(b) instead; certain subclasses of FilterInputStream depend on the implementation strategy actually used.

      Overrides:
      read in class InputStream
      Parameters:
      b - the buffer into which the data is read.
      Returns:
      the total number of bytes read into the buffer, or -1 if there is no more data because the end of the stream has been reached.
      Throws:
      IOException - if an I/O error occurs.
      See Also:
      read(byte[], int, int)

    • read

      public int read​(byte[] b, int off, int len) throws IOException
      Reads up to len bytes of data from this input stream into an array of bytes. If len is not zero, the method blocks until some input is available; otherwise, no bytes are read and 0 is returned.

      This method simply performs in.read(b, off, len) and returns the result.

      Overrides:
      read in class InputStream
      Parameters:
      b - the buffer into which the data is read.
      off - the start offset in the destination array b
      len - the maximum number of bytes read.
      Returns:
      the total number of bytes read into the buffer, or -1 if there is no more data because the end of the stream has been reached.
      Throws:
      NullPointerException - If b is null.
      IndexOutOfBoundsException - If off is negative, len is negative, or len is greater than b.length - off
      IOException - if an I/O error occurs.
      See Also:
      in

    • skip

      public long skip​(long n) throws IOException
      Skips over and discards n bytes of data from the input stream. The skip method may, for a variety of reasons, end up skipping over some smaller number of bytes, possibly 0. The actual number of bytes skipped is returned.

      This method simply performs in.skip(n).

      Overrides:
      skip in class InputStream
      Parameters:
      n - the number of bytes to be skipped.
      Returns:
      the actual number of bytes skipped.
      Throws:
      IOException - if in.skip(n) throws an IOException.
      See Also:
      InputStream.skipNBytes(long)

    • available

      public int available() throws IOException
      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. The next caller might be the same thread or another thread. A single read or skip of this many bytes will not block, but may read or skip fewer bytes.

      This method returns the result of in.available().

      Overrides:
      available in class InputStream
      Returns:
      an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking.
      Throws:
      IOException - if an I/O error occurs.

    • close

      public void close() throws IOException
      Closes this input stream and releases any system resources associated with the stream. This method simply performs in.close().
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Overrides:
      close in class InputStream
      Throws:
      IOException - if an I/O error occurs.
      See Also:
      in

    • mark

      public void mark​(int readlimit)
      Marks the current position in this input stream. A subsequent call to the reset method repositions this stream at the last marked position so that subsequent reads re-read the same bytes.

      The readlimit argument tells this input stream to allow that many bytes to be read before the mark position gets invalidated.

      This method simply performs in.mark(readlimit).

      Overrides:
      mark in class InputStream
      Parameters:
      readlimit - the maximum limit of bytes that can be read before the mark position becomes invalid.
      See Also:
      in, reset()

    • reset

      public void reset() throws IOException
      Repositions this stream to the position at the time the mark method was last called on this input stream.

      This method simply performs in.reset().

      Stream marks are intended to be used in situations where you need to read ahead a little to see what's in the stream. Often this is most easily done by invoking some general parser. If the stream is of the type handled by the parse, it just chugs along happily. If the stream is not of that type, the parser should toss an exception when it fails. If this happens within readlimit bytes, it allows the outer code to reset the stream and try another parser.

      Overrides:
      reset in class InputStream
      Throws:
      IOException - if the stream has not been marked or if the mark has been invalidated.
      See Also:
      in, mark(int)

    • markSupported

      public boolean markSupported()
      Tests if this input stream supports the mark and reset methods. This method simply performs in.markSupported().
      Overrides:
      markSupported in class InputStream
      Returns:
      true if this stream type supports the mark and reset method; false otherwise.
      See Also:
      in, InputStream.mark(int), InputStream.reset()