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.
BufferedReader, LineNumberReader, CharArrayReader, InputStreamReader, FileReader, FilterReader, PushbackReader, PipedReader, StringReader, Writer
protected Object lock
The object used to synchronize operations on this stream.
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.
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.
int read(CharBuffer target)
Attempts to read characters into the specified character buffer.
boolean ready()
Tells whether this stream is ready to be read.
void reset()
Resets the stream.
long skip(long n)
Skips characters.
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.
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.
lock - The Object to synchronize on.
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.
read in interface Readable
target - the buffer to read characters into
IOException - if an I/O error occurs
NullPointerException - if target is null
ReadOnlyBufferException - if target is a read only buffer
public int read()
throws IOException
Subclasses that intend to support efficient single-character input should override this method.
IOException - If an I/O error occurs
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.
cbuf - Destination buffer
IOException - If an I/O error occurs
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.
cbuf - Destination buffer
off - Offset at which to start storing characters
len - Maximum number of characters to read
IOException - If an I/O error occurs
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.
n - The number of characters to skip
IllegalArgumentException - If n is negative.
IOException - If an I/O error occurs
public boolean ready()
throws IOException
Tells whether this stream is ready to be read.
IOException - If an I/O error occurs
public boolean markSupported()
Tells whether this stream supports the mark() operation. The default implementation always returns false. Subclasses should override this method.
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.
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.
IOException - If the stream does not support mark(), or if some other I/O error occurs
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().
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
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.
close in interface Closeable
close in interface AutoCloseable
IOException - If an I/O error occurs
Submit a bug or feature
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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