Module java.base
Package java.io

Class FilterReader

java.lang.Object
java.io.Reader
java.io.FilterReader
All Implemented Interfaces:
Closeable, AutoCloseable, Readable
Direct Known Subclasses:
PushbackReader

public abstract class FilterReader extends Reader
Abstract class for reading filtered character streams. The abstract class FilterReader itself provides default methods that pass all requests to the contained stream. Subclasses of FilterReader should override some of these methods and may also provide additional methods and fields.
Since:
1.1
  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    protected Reader
    The underlying character-input stream.

    Fields declared in class java.io.Reader

    lock
  • Constructor Summary

    Constructors
    Modifier
    Constructor
    Description
    protected
    Creates a new filtered reader.
  • Method Summary

    Modifier and Type
    Method
    Description
    void
    Closes the stream and releases any system resources associated with it.
    void
    mark​(int readAheadLimit)
    Marks the present position in the stream.
    boolean
    Tells whether this stream supports the mark() operation.
    int
    Reads a single character.
    int
    read​(char[] cbuf, int off, int len)
    Reads characters into a portion of an array.
    boolean
    Tells whether this stream is ready to be read.
    void
    Resets the stream.
    long
    skip​(long n)
    Skips characters.

    Methods declared in class java.io.Reader

    nullReader, read, read, transferTo

    Methods declared in class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
  • Field Details

    • in

      protected Reader in
      The underlying character-input stream.
  • Constructor Details

    • FilterReader

      protected FilterReader(Reader in)
      Creates a new filtered reader.
      Parameters:
      in - a Reader object providing the underlying stream.
      Throws:
      NullPointerException - if in is null
  • Method Details

    • read

      public int read() throws IOException
      Reads a single character.
      Overrides:
      read in class Reader
      Returns:
      The character read, as an integer in the range 0 to 65535 (0x00-0xffff), or -1 if the end of the stream has been reached
      Throws:
      IOException - If an I/O error occurs
    • read

      public int read(char[] cbuf, int off, int len) throws IOException
      Reads characters into a portion of an array. This method will block until some input is available, an I/O error occurs, or the end of the stream is reached.

      If len is zero, then no characters are read and 0 is returned; otherwise, there is an attempt to read at least one character. If no character is available because the stream is at its end, the value -1 is returned; otherwise, at least one character is read and stored into cbuf.

      Specified by:
      read in class Reader
      Parameters:
      cbuf - Destination buffer
      off - Offset at which to start storing characters
      len - Maximum number of characters to read
      Returns:
      The number of characters read, or -1 if the end of the stream has been reached
      Throws:
      IndexOutOfBoundsException - If off is negative, or len is negative, or len is greater than cbuf.length - off
      IOException - If an I/O error occurs
    • skip

      public long skip(long n) throws IOException
      Skips characters. This method will block until some characters are available, an I/O error occurs, or the end of the stream is reached. If the stream is already at its end before this method is invoked, then no characters are skipped and zero is returned.
      Overrides:
      skip in class Reader
      Parameters:
      n - The number of characters to skip
      Returns:
      The number of characters actually skipped
      Throws:
      IllegalArgumentException - If n is negative and the contained Reader's skip method throws an IllegalArgumentException for a negative parameter
      IOException - If an I/O error occurs
    • ready

      public boolean ready() throws IOException
      Tells whether this stream is ready to be read.
      Overrides:
      ready in class Reader
      Returns:
      True if the next read() is guaranteed not to block for input, false otherwise. Note that returning false does not guarantee that the next read will block.
      Throws:
      IOException - If an I/O error occurs
    • markSupported

      public boolean markSupported()
      Tells whether this stream supports the mark() operation.
      Overrides:
      markSupported in class Reader
      Returns:
      true if and only if this stream supports the mark operation.
    • mark

      public void mark(int readAheadLimit) throws IOException
      Marks the present position in the stream.
      Overrides:
      mark in class Reader
      Parameters:
      readAheadLimit - Limit on the number of characters that may be read while still preserving the mark. After reading this many characters, attempting to reset the stream may fail.
      Throws:
      IOException - If an I/O error occurs
    • reset

      public void reset() throws IOException
      Resets the stream.
      Overrides:
      reset in class Reader
      Throws:
      IOException - If an I/O error occurs
    • close

      public void close() throws IOException
      Description copied from class: Reader
      Closes the stream and releases any system resources associated with it. Once the stream has been closed, further read(), ready(), mark(), reset(), or skip() invocations will throw an IOException. Closing a previously closed stream has no effect.
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Specified by:
      close in class Reader
      Throws:
      IOException - If an I/O error occurs