java.io.Reader Maven / Gradle / Ivy
/*
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stub files, must be accompanied by this notice in its entirety.
This work corresponds to the API signatures of JSR 219: Foundation
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JSR 219 specification, which is available at
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*/
package java.io;
/**
* 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 BufferedReader
* @see LineNumberReader
* @see CharArrayReader
* @see InputStreamReader
* @see FileReader
* @see FilterReader
* @see PushbackReader
* @see PipedReader
* @see StringReader
* @see Writer
*
* @version 1.21, 00/02/02
* @author Mark Reinhold
* @since JDK1.1
*/
public abstract class Reader
{
/**
* 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 Object lock;
/**
* Create a new character-stream reader whose critical sections will
* synchronize on the reader itself.
*/
protected Reader() { }
/**
* Create a new character-stream reader whose critical sections will
* synchronize on the given object.
*
* @param lock The Object to synchronize on.
*/
protected Reader(Object lock) { }
/**
* 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 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
*
* @exception IOException If an I/O error occurs
*/
public int read() throws IOException {
return 0;
}
/**
* 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.
*
* @param cbuf Destination buffer
*
* @return The number of characters read, or -1
* if the end of the stream
* has been reached
*
* @exception IOException If an I/O error occurs
*/
public int read(char[] cbuf) throws IOException {
return 0;
}
/**
* 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.
*
* @param cbuf Destination buffer
* @param off Offset at which to start storing characters
* @param len Maximum number of characters to read
*
* @return The number of characters read, or -1 if the end of the
* stream has been reached
*
* @exception IOException If an I/O error occurs
*/
public abstract int read(char[] cbuf, int off, int len) 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.
*
* @param n The number of characters to skip
*
* @return The number of characters actually skipped
*
* @exception IllegalArgumentException If n is negative.
* @exception IOException If an I/O error occurs
*/
public long skip(long n) throws IOException {
return -1;
}
/**
* Tell whether this stream is ready to be read.
*
* @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.
*
* @exception IOException If an I/O error occurs
*/
public boolean ready() throws IOException {
return false;
}
/**
* Tell whether this stream supports the mark() operation. The default
* implementation always returns false. Subclasses should override this
* method.
*
* @return true if and only if this stream supports the mark operation.
*/
public boolean markSupported() {
return false;
}
/**
* 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.
*
* @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.
*
* @exception IOException If the stream does not support mark(),
* or if some other I/O error occurs
*/
public void mark(int readAheadLimit) 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().
*
* @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
*/
public void reset() 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.
*
* @exception IOException If an I/O error occurs
*/
public abstract void close() throws IOException;
}