Class: java.io.Reader

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.
Authors:
@author Mark Reinhold
See:
@see java.io.BufferedReader
@see java.io.LineNumberReader
@see java.io.CharArrayReader
@see java.io.InputStreamReader
@see java.io.FileReader
@see java.io.FilterReader
@see java.io.PushbackReader
@see java.io.PipedReader
@see java.io.StringReader
@see java.io.Writer
Version:
@version 1.27, 03/12/19
Since:
@since JDK1.1

Inheritance

Superclass tree: Implements:

Methods

  • Readertop

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

    protected Reader(Object lock)
    Create a new character-stream reader whose critical sections will synchronize on the given object.
    Parameters:
    @param lock The Object to synchronize on.
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  • closetop

    public abstract void close() throws IOException
    Close the stream. Once a stream has been closed, further read(), ready(), mark(), or reset() invocations will throw an IOException. Closing a previously-closed stream, however, has no effect.
    Exceptions:
    @exception IOException If an I/O error occurs
    Specified by:
    close from Closeable
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  • marktop

    public void mark(int readAheadLimit) throws IOException
    Mark 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:
    @param 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.
    Exceptions:
    @exception IOException If the stream does not support mark(), or if some other I/O error occurs
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  • markSupportedtop

    public boolean markSupported()
    Tell whether this stream supports the mark() operation. The default implementation always returns false. Subclasses should override this method.
    Return:
    @return true if and only if this stream supports the mark operation.
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  • readtop

    public int read() throws IOException
    Read 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.

    Return:
    @return 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
    Exceptions:
    @exception IOException If an I/O error occurs
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  • readtop

    public int read(CharBuffer target) throws IOException
    Attempts to read characters into the specified character buffer. The buffer is used as a repository of characters as-is: the only changes made are the results of a put operation. No flipping or rewinding of the buffer is performed.
    Parameters:
    @param target the buffer to read characters into
    Return:
    @return The number of characters added to the buffer, or -1 if this source of characters is at its end
    Exceptions:
    @throws IOException if an I/O error occurs
    @throws NullPointerException if target is null
    @throws ReadOnlyBufferException if target is a read only buffer
    Specified by:
    read from Readable
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  • readtop

    public int read(char[] cbuf) throws IOException
    Read 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:
    @param cbuf Destination buffer
    Return:
    @return The number of characters read, or -1 if the end of the stream has been reached
    Exceptions:
    @exception IOException If an I/O error occurs
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  • readtop

    public abstract int read(char[] cbuf, int off, int len) throws IOException
    Read 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:
    @param cbuf Destination buffer
    @param off Offset at which to start storing characters
    @param len Maximum number of characters to read
    Return:
    @return The number of characters read, or -1 if the end of the stream has been reached
    Exceptions:
    @exception IOException If an I/O error occurs
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  • readytop

    public boolean ready() throws IOException
    Tell whether this stream is ready to be read.
    Return:
    @return 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.
    Exceptions:
    @exception IOException If an I/O error occurs
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  • resettop

    public void reset() throws IOException
    Reset 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().
    Exceptions:
    @exception 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
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  • skiptop

    public long skip(long n) throws IOException
    Skip characters. This method will block until some characters are available, an I/O error occurs, or the end of the stream is reached.
    Parameters:
    @param n The number of characters to skip
    Return:
    @return The number of characters actually skipped
    Exceptions:
    @exception IllegalArgumentException If n is negative.
    @exception IOException If an I/O error occurs
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Fields

  • lock

    protected Object lock
    The object used to synchronize operations on this stream. For efficiency, a character-stream object may use an object other than itself to protect critical sections. A subclass should therefore use the object in this field rather than this or a synchronized method.