Module java.base
Package java.io

Class PushbackReader

    • Constructor Summary

      Constructors 
      Constructor Description
      PushbackReader​(Reader in)
      Creates a new pushback reader with a one-character pushback buffer.
      PushbackReader​(Reader in, int size)
      Creates a new pushback reader with a pushback buffer of the given size.
    • Method Summary

      Modifier and Type Method Description
      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, which it does not.
      int read()
      Reads a single character.
      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.
      void unread​(char[] cbuf)
      Pushes back an array of characters by copying it to the front of the pushback buffer.
      void unread​(char[] cbuf, int off, int len)
      Pushes back a portion of an array of characters by copying it to the front of the pushback buffer.
      void unread​(int c)
      Pushes back a single character by copying it to the front of the pushback buffer.
    • Constructor Detail

      • PushbackReader

        public PushbackReader​(Reader in,
                              int size)
        Creates a new pushback reader with a pushback buffer of the given size.
        Parameters:
        in - The reader from which characters will be read
        size - The size of the pushback buffer
        Throws:
        IllegalArgumentException - if size <= 0
      • PushbackReader

        public PushbackReader​(Reader in)
        Creates a new pushback reader with a one-character pushback buffer.
        Parameters:
        in - The reader from which characters will be read
    • Method Detail

      • read

        public int read()
                 throws IOException
        Reads a single character.
        Overrides:
        read in class FilterReader
        Returns:
        The character read, 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.
        Overrides:
        read in class FilterReader
        Parameters:
        cbuf - Destination buffer
        off - Offset at which to start writing 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
        IndexOutOfBoundsException - If an I/O error occurs
      • unread

        public void unread​(int c)
                    throws IOException
        Pushes back a single character by copying it to the front of the pushback buffer. After this method returns, the next character to be read will have the value (char)c.
        Parameters:
        c - The int value representing a character to be pushed back
        Throws:
        IOException - If the pushback buffer is full, or if some other I/O error occurs
      • unread

        public void unread​(char[] cbuf,
                           int off,
                           int len)
                    throws IOException
        Pushes back a portion of an array of characters by copying it to the front of the pushback buffer. After this method returns, the next character to be read will have the value cbuf[off], the character after that will have the value cbuf[off+1], and so forth.
        Parameters:
        cbuf - Character array
        off - Offset of first character to push back
        len - Number of characters to push back
        Throws:
        IOException - If there is insufficient room in the pushback buffer, or if some other I/O error occurs
      • unread

        public void unread​(char[] cbuf)
                    throws IOException
        Pushes back an array of characters by copying it to the front of the pushback buffer. After this method returns, the next character to be read will have the value cbuf[0], the character after that will have the value cbuf[1], and so forth.
        Parameters:
        cbuf - Character array to push back
        Throws:
        IOException - If there is insufficient room in the pushback buffer, or if some other I/O error occurs
      • ready

        public boolean ready()
                      throws IOException
        Tells whether this stream is ready to be read.
        Overrides:
        ready in class FilterReader
        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
      • mark

        public void mark​(int readAheadLimit)
                  throws IOException
        Marks the present position in the stream. The mark for class PushbackReader always throws an exception.
        Overrides:
        mark in class FilterReader
        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 - Always, since mark is not supported
      • reset

        public void reset()
                   throws IOException
        Resets the stream. The reset method of PushbackReader always throws an exception.
        Overrides:
        reset in class FilterReader
        Throws:
        IOException - Always, since reset is not supported
      • markSupported

        public boolean markSupported()
        Tells whether this stream supports the mark() operation, which it does not.
        Overrides:
        markSupported in class FilterReader
        Returns:
        true if and only if this stream supports the mark operation.
      • close

        public void close()
                   throws IOException
        Closes the stream and releases any system resources associated with it. Once the stream has been closed, further read(), unread(), ready(), or skip() invocations will throw an IOException. Closing a previously closed stream has no effect. This method will block while there is another thread blocking on the reader.
        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
      • 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.
        Overrides:
        skip in class FilterReader
        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