Package java.io

Class FilterReader

  • All Implemented Interfaces:
    Closeable, AutoCloseable, Readable
    Direct Known Subclasses:
    PushbackReader
    public abstract class FilterReader
extends Reader
    Wraps an existing Reader and performs some transformation on the input data while it is being read. Transformations can be anything from a simple byte-wise filtering input data to an on-the-fly compression or decompression of the underlying reader. Readers that wrap another reader and provide some additional functionality on top of it usually inherit from this class.
    See Also:
    FilterWriter

    • Field Summary

      Fields 
      Modifier and Type Field Description
      protected Reader in
      The target Reader which is being filtered.

    • Constructor Summary

      Constructors 
      Modifier Constructor Description
      protected FilterReader​(Reader in)
      Constructs a new FilterReader on the Reader in.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void close()
      Closes this reader.
      void mark​(int readlimit)
      Sets a mark position in this reader.
      boolean markSupported()
      Indicates whether this reader supports mark() and reset().
      int read()
      Reads a single character from the filtered reader and returns it as an integer with the two higher-order bytes set to 0.
      int read​(char[] buffer, int offset, int count)
      Reads up to count characters from the filtered reader and stores them in the byte array buffer starting at offset.
      boolean ready()
      Indicates whether this reader is ready to be read without blocking.
      void reset()
      Resets this reader's position to the last marked location.
      long skip​(long charCount)
      Skips charCount characters in this reader.

    • Field Detail

      • in

        protected Reader in
        The target Reader which is being filtered.

    • Constructor Detail

      • FilterReader

        protected FilterReader​(Reader in)
        Constructs a new FilterReader on the Reader in.
        Parameters:
        in - The non-null Reader to filter reads on.

    • Method Detail

      • mark

        public void mark​(int readlimit)
          throws IOException
        Sets a mark position in this reader. The parameter readlimit indicates how many bytes can be read before the mark is invalidated. Sending reset() will reposition this reader back to the marked position, provided that readlimit has not been surpassed.

        This implementation sets a mark in the filtered reader.

        Overrides:
        mark in class Reader
        Parameters:
        readlimit - the number of bytes that can be read from this reader before the mark is invalidated.
        Throws:
        IOException - if an error occurs while marking this reader.
        See Also:
        markSupported(), reset()

      • markSupported

        public boolean markSupported()
        Indicates whether this reader supports mark() and reset(). This implementation returns whether the filtered reader supports marking.
        Overrides:
        markSupported in class Reader
        Returns:
        true if mark() and reset() are supported by the filtered reader, false otherwise.
        See Also:
        mark(int), reset(), skip(long)

      • read

        public int read()
         throws IOException
        Reads a single character from the filtered reader and returns it as an integer with the two higher-order bytes set to 0. Returns -1 if the end of the filtered reader has been reached.
        Overrides:
        read in class Reader
        Returns:
        The character read or -1 if the end of the filtered reader has been reached.
        Throws:
        IOException - if an error occurs while reading from this reader.

      • read

        public int read​(char[] buffer,
                int offset,
                int count)
         throws IOException
        Reads up to count characters from the filtered reader and stores them in the byte array buffer starting at offset. Returns the number of characters actually read or -1 if no characters were read and the end of the filtered reader was encountered.
        Specified by:
        read in class Reader
        Throws:
        IOException - if an error occurs while reading from this reader.

      • ready

        public boolean ready()
              throws IOException
        Indicates whether this reader is ready to be read without blocking. If the result is true, the next read() will not block. If the result is false, this reader may or may not block when read() is sent.
        Overrides:
        ready in class Reader
        Returns:
        true if this reader will not block when read() is called, false if unknown or blocking will occur.
        Throws:
        IOException - if the reader is closed or some other I/O error occurs.
        See Also:
        Reader.read(), Reader.read(char[]), Reader.read(char[], int, int)

      • reset

        public void reset()
           throws IOException
        Resets this reader's position to the last marked location. Invocations of read() and skip() will occur from this new location. If this reader was not marked, the behavior depends on the implementation of reset() in the Reader subclass that is filtered by this reader. The default behavior for Reader is to throw an IOException.
        Overrides:
        reset in class Reader
        Throws:
        IOException - if a problem occurred or the filtered reader does not support mark() and reset().
        See Also:
        mark(int), markSupported()

      • skip

        public long skip​(long charCount)
          throws IOException
        Skips charCount characters in this reader. Subsequent calls to read will not return these characters unless reset is used. The default implementation is to skip characters in the filtered reader.
        Overrides:
        skip in class Reader
        Returns:
        the number of characters actually skipped.
        Throws:
        IOException - if the filtered reader is closed or some other I/O error occurs.
        See Also:
        mark(int), markSupported(), reset()