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 {
+ char cb[] = new char[1];
+ if (read(cb, 0, 1) == -1)
+ return -1;
+ else
+ return cb[0];
+ }
+
+ /**
+ * 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.
+ *
+ * @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 read(cbuf, 0, cbuf.length);
+ }
+
+ /**
+ * 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.
+ *
+ * @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
+ */
+ abstract public int read(char cbuf[], int off, int len) throws IOException;
+
+ /** Maximum skip-buffer size */
+ private static final int maxSkipBufferSize = 8192;
+
+ /** Skip buffer, null until allocated */
+ private char skipBuffer[] = null;
+
+ /**
+ * Skips 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 {
+ if (n < 0L)
+ throw new IllegalArgumentException("skip value is negative");
+ int nn = (int) Math.min(n, maxSkipBufferSize);
+ synchronized (lock) {
+ if ((skipBuffer == null) || (skipBuffer.length < nn))
+ skipBuffer = new char[nn];
+ long r = n;
+ while (r > 0) {
+ int nc = read(skipBuffer, 0, (int)Math.min(r, nn));
+ if (nc == -1)
+ break;
+ r -= nc;
+ }
+ return n - r;
+ }
+ }
+
+ /**
+ * Tells 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;
+ }
+
+ /**
+ * Tells 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;
+ }
+
+ /**
+ * 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.
+ *
+ * @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 {
+ throw new IOException("mark() not supported");
+ }
+
+ /**
+ * 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().
+ *
+ * @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 {
+ throw new IOException("reset() not supported");
+ }
+
+ /**
+ * 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.
+ *
+ * @exception IOException If an I/O error occurs
+ */
+ abstract public void close() throws IOException;
+
+}