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28 import java.nio.charset.Charset;
29 import java.nio.charset.CharsetDecoder;
30 import sun.nio.cs.StreamDecoder;
34 * An InputStreamReader is a bridge from byte streams to character streams: It
35 * reads bytes and decodes them into characters using a specified {@link
36 * java.nio.charset.Charset <code>charset</code>}. The charset that it uses
37 * may be specified by name or may be given explicitly, or the platform's
38 * default charset may be accepted.
40 * <p> Each invocation of one of an InputStreamReader's read() methods may
41 * cause one or more bytes to be read from the underlying byte-input stream.
42 * To enable the efficient conversion of bytes to characters, more bytes may
43 * be read ahead from the underlying stream than are necessary to satisfy the
44 * current read operation.
46 * <p> For top efficiency, consider wrapping an InputStreamReader within a
47 * BufferedReader. For example:
51 * = new BufferedReader(new InputStreamReader(System.in));
56 * @see java.nio.charset.Charset
58 * @author Mark Reinhold
62 public class InputStreamReader extends Reader {
64 private final StreamDecoder sd;
67 * Creates an InputStreamReader that uses the default charset.
69 * @param in An InputStream
71 public InputStreamReader(InputStream in) {
74 sd = StreamDecoder.forInputStreamReader(in, this, (String)null); // ## check lock object
75 } catch (UnsupportedEncodingException e) {
76 // The default encoding should always be available
82 * Creates an InputStreamReader that uses the named charset.
88 * The name of a supported
89 * {@link java.nio.charset.Charset </code>charset<code>}
91 * @exception UnsupportedEncodingException
92 * If the named charset is not supported
94 public InputStreamReader(InputStream in, String charsetName)
95 throws UnsupportedEncodingException
98 if (charsetName == null)
99 throw new NullPointerException("charsetName");
100 sd = StreamDecoder.forInputStreamReader(in, this, charsetName);
104 * Creates an InputStreamReader that uses the given charset. </p>
106 * @param in An InputStream
107 * @param cs A charset
113 public InputStreamReader(InputStream in, Charset cs) {
116 throw new NullPointerException("charset");
117 sd = StreamDecoder.forInputStreamReader(in, this, cs);
121 * Creates an InputStreamReader that uses the given charset decoder. </p>
123 * @param in An InputStream
124 * @param dec A charset decoder
130 public InputStreamReader(InputStream in, CharsetDecoder dec) {
133 throw new NullPointerException("charset decoder");
134 sd = StreamDecoder.forInputStreamReader(in, this, dec);
139 * Returns the name of the character encoding being used by this stream.
141 * <p> If the encoding has an historical name then that name is returned;
142 * otherwise the encoding's canonical name is returned.
144 * <p> If this instance was created with the {@link
145 * #InputStreamReader(InputStream, String)} constructor then the returned
146 * name, being unique for the encoding, may differ from the name passed to
147 * the constructor. This method will return <code>null</code> if the
148 * stream has been closed.
150 * @return The historical name of this encoding, or
151 * <code>null</code> if the stream has been closed
153 * @see java.nio.charset.Charset
158 public String getEncoding() {
159 return sd.getEncoding();
163 * Reads a single character.
165 * @return The character read, or -1 if the end of the stream has been
168 * @exception IOException If an I/O error occurs
170 public int read() throws IOException {
175 * Reads characters into a portion of an array.
177 * @param cbuf Destination buffer
178 * @param offset Offset at which to start storing characters
179 * @param length Maximum number of characters to read
181 * @return The number of characters read, or -1 if the end of the
182 * stream has been reached
184 * @exception IOException If an I/O error occurs
186 public int read(char cbuf[], int offset, int length) throws IOException {
187 return sd.read(cbuf, offset, length);
191 * Tells whether this stream is ready to be read. An InputStreamReader is
192 * ready if its input buffer is not empty, or if bytes are available to be
193 * read from the underlying byte stream.
195 * @exception IOException If an I/O error occurs
197 public boolean ready() throws IOException {
201 public void close() throws IOException {