Package java.io

Class Reader

  • All Implemented Interfaces:
    Closeable, AutoCloseable, Readable
    Direct Known Subclasses:
    InputStreamReader
    public abstract class Reader
extends Object
implements Readable, Closeable
    Abstract class for reading character streams. The only methods that a subclass must implement are read(char[], int, int) and close(). Most subclasses, however, will override some of the methods defined here in order to provide higher efficiency, additional functionality, or both.
    See Also:
    InputStreamReader, Writer

    • Constructor Summary

      Constructors 
      Modifier Constructor Description
      protected Reader()
      Creates a new character-stream reader whose critical sections will synchronize on the reader itself.
      protected Reader​(Object lock)
      Creates a new character-stream reader whose critical sections will synchronize on the given object.

    • Method Summary

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

    • Constructor Detail

      • Reader

        protected Reader()
        Creates a new character-stream reader whose critical sections will synchronize on the reader itself.

      • Reader

        protected Reader​(Object lock)
        Creates a new character-stream reader whose critical sections will synchronize on the given object.
        Parameters:
        lock - The Object to synchronize on.

    • Method Detail

      • close

        public abstract void close()
                    throws IOException
        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
        Throws:
        IOException - If an I/O error occurs

      • mark

        public void mark​(int readAheadLimit)
          throws IOException
        Marks the present position in the stream. Subsequent calls to reset() will attempt to reposition the stream to this point. Not all character-input streams support the mark() operation.
        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 the stream does not support mark(), or if some other I/O error occurs

      • markSupported

        public boolean markSupported()
        Tells whether this stream supports the mark() operation. The default implementation always returns false. Subclasses should override this method.
        Returns:
        true if and only if this stream supports the mark operation.

      • read

        public int read()
         throws IOException
        Reads a single character. This method will block until a character is available, an I/O error occurs, or the end of the stream is reached.

        Subclasses that intend to support efficient single-character input should override this method.

        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)
         throws IOException
        Reads characters into an array. This method will block until some input is available, an I/O error occurs, or the end of the stream is reached.
        Parameters:
        cbuf - Destination buffer
        Returns:
        The number of characters read, or -1 if the end of the stream has been reached
        Throws:
        IOException - If an I/O error occurs

      • read

        public abstract 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.
        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:
        IOException - If an I/O error occurs

      • ready

        public boolean ready()
              throws IOException
        Tells whether this stream is ready to be read.
        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

      • reset

        public void reset()
           throws IOException
        Resets the stream. If the stream has been marked, then attempt to reposition it at the mark. If the stream has not been marked, then attempt to reset it in some way appropriate to the particular stream, for example by repositioning it to its starting point. Not all character-input streams support the reset() operation, and some support reset() without supporting mark().
        Throws:
        IOException - If the stream has not been marked, or if the mark has been invalidated, or if the stream does not support reset(), or if some other 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.
        Parameters:
        n - The number of characters to skip
        Returns:
        The number of characters actually skipped
        Throws:
        IllegalArgumentException - If n is negative.
        IOException - If an I/O error occurs