Showing the changes to java/pkg/java/io/DataInput.java (1 of 18352 files). Show all
Unified · Split
| @@ -0,0 +1,635 @@ | |||
| 1 | /* | ||
| 2 | * Copyright (c) 1995, 2006, Oracle and/or its affiliates. All rights reserved. | ||
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | ||
| 4 | * | ||
| 5 | * This code is free software; you can redistribute it and/or modify it | ||
| 6 | * under the terms of the GNU General Public License version 2 only, as | ||
| 7 | * published by the Free Software Foundation. Oracle designates this | ||
| 8 | * particular file as subject to the "Classpath" exception as provided | ||
| 9 | * by Oracle in the LICENSE file that accompanied this code. | ||
| 10 | * | ||
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT | ||
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | ||
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | ||
| 14 | * version 2 for more details (a copy is included in the LICENSE file that | ||
| 15 | * accompanied this code). | ||
| 16 | * | ||
| 17 | * You should have received a copy of the GNU General Public License version | ||
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, | ||
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | ||
| 20 | * | ||
| 21 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | ||
| 22 | * or visit www.oracle.com if you need additional information or have any | ||
| 23 | * questions. | ||
| 24 | */ | ||
| 25 | |||
| 26 | package java.io; | ||
| 27 | |||
| 28 | /** | ||
| 29 | * The <code>DataInput</code> interface provides | ||
| 30 | * for reading bytes from a binary stream and | ||
| 31 | * reconstructing from them data in any of | ||
| 32 | * the Java primitive types. There is also | ||
| 33 | * a | ||
| 34 | * facility for reconstructing a <code>String</code> | ||
| 35 | * from data in | ||
| 36 | * <a href="#modified-utf-8">modified UTF-8</a> | ||
| 37 | * format. | ||
| 38 | * <p> | ||
| 39 | * It is generally true of all the reading | ||
| 40 | * routines in this interface that if end of | ||
| 41 | * file is reached before the desired number | ||
| 42 | * of bytes has been read, an <code>EOFException</code> | ||
| 43 | * (which is a kind of <code>IOException</code>) | ||
| 44 | * is thrown. If any byte cannot be read for | ||
| 45 | * any reason other than end of file, an <code>IOException</code> | ||
| 46 | * other than <code>EOFException</code> is | ||
| 47 | * thrown. In particular, an <code>IOException</code> | ||
| 48 | * may be thrown if the input stream has been | ||
| 49 | * closed. | ||
| 50 | * | ||
| 51 | * <h4><a name="modified-utf-8">Modified UTF-8</a></h4> | ||
| 52 | * <p> | ||
| 53 | * Implementations of the DataInput and DataOutput interfaces represent | ||
| 54 | * Unicode strings in a format that is a slight modification of UTF-8. | ||
| 55 | * (For information regarding the standard UTF-8 format, see section | ||
| 56 | * <i>3.9 Unicode Encoding Forms</i> of <i>The Unicode Standard, Version | ||
| 57 | * 4.0</i>). | ||
| 58 | * Note that in the following tables, the most significant bit appears in the | ||
| 59 | * far left-hand column. | ||
| 60 | * <p> | ||
| 61 | * All characters in the range <code>'\u0001'</code> to | ||
| 62 | * <code>'\u007F'</code> are represented by a single byte: | ||
| 63 | * | ||
| 64 | * <blockquote> | ||
| 65 | * <table border="1" cellspacing="0" cellpadding="8" width="50%" | ||
| 66 | * summary="Bit values and bytes"> | ||
| 67 | * <tr> | ||
| 68 | * <td></td> | ||
| 69 | * <th id="bit">Bit Values</th> | ||
| 70 | * </tr> | ||
| 71 | * <tr> | ||
| 72 | * <th id="byte1">Byte 1</th> | ||
| 73 | * <td> | ||
| 74 | * <table border="1" cellspacing="0" width="100%"> | ||
| 75 | * <tr> | ||
| 76 | * <td width="12%"><center>0</center> | ||
| 77 | * <td colspan="7"><center>bits 6-0</center> | ||
| 78 | * </tr> | ||
| 79 | * </table> | ||
| 80 | * </td> | ||
| 81 | * </tr> | ||
| 82 | * </table> | ||
| 83 | * </blockquote> | ||
| 84 | * | ||
| 85 | * <p> | ||
| 86 | * The null character <code>'\u0000'</code> and characters in the | ||
| 87 | * range <code>'\u0080'</code> to <code>'\u07FF'</code> are | ||
| 88 | * represented by a pair of bytes: | ||
| 89 | * | ||
| 90 | * <blockquote> | ||
| 91 | * <table border="1" cellspacing="0" cellpadding="8" width="50%" | ||
| 92 | * summary="Bit values and bytes"> | ||
| 93 | * <tr> | ||
| 94 | * <td></td> | ||
| 95 | * <th id="bit">Bit Values</th> | ||
| 96 | * </tr> | ||
| 97 | * <tr> | ||
| 98 | * <th id="byte1">Byte 1</th> | ||
| 99 | * <td> | ||
| 100 | * <table border="1" cellspacing="0" width="100%"> | ||
| 101 | * <tr> | ||
| 102 | * <td width="12%"><center>1</center> | ||
| 103 | * <td width="13%"><center>1</center> | ||
| 104 | * <td width="12%"><center>0</center> | ||
| 105 | * <td colspan="5"><center>bits 10-6</center> | ||
| 106 | * </tr> | ||
| 107 | * </table> | ||
| 108 | * </td> | ||
| 109 | * </tr> | ||
| 110 | * <tr> | ||
| 111 | * <th id="byte2">Byte 2</th> | ||
| 112 | * <td> | ||
| 113 | * <table border="1" cellspacing="0" width="100%"> | ||
| 114 | * <tr> | ||
| 115 | * <td width="12%"><center>1</center> | ||
| 116 | * <td width="13%"><center>0</center> | ||
| 117 | * <td colspan="6"><center>bits 5-0</center> | ||
| 118 | * </tr> | ||
| 119 | * </table> | ||
| 120 | * </td> | ||
| 121 | * </tr> | ||
| 122 | * </table> | ||
| 123 | * </blockquote> | ||
| 124 | * | ||
| 125 | * <br> | ||
| 126 | * <code>char</code> values in the range <code>'\u0800'</code> to | ||
| 127 | * <code>'\uFFFF'</code> are represented by three bytes: | ||
| 128 | * | ||
| 129 | * <blockquote> | ||
| 130 | * <table border="1" cellspacing="0" cellpadding="8" width="50%" | ||
| 131 | * summary="Bit values and bytes"> | ||
| 132 | * <tr> | ||
| 133 | * <td></td> | ||
| 134 | * <th id="bit">Bit Values</th> | ||
| 135 | * </tr> | ||
| 136 | * <tr> | ||
| 137 | * <th id="byte1">Byte 1</th> | ||
| 138 | * <td> | ||
| 139 | * <table border="1" cellspacing="0" width="100%"> | ||
| 140 | * <tr> | ||
| 141 | * <td width="12%"><center>1</center> | ||
| 142 | * <td width="13%"><center>1</center> | ||
| 143 | * <td width="12%"><center>1</center> | ||
| 144 | * <td width="13%"><center>0</center> | ||
| 145 | * <td colspan="4"><center>bits 15-12</center> | ||
| 146 | * </tr> | ||
| 147 | * </table> | ||
| 148 | * </td> | ||
| 149 | * </tr> | ||
| 150 | * <tr> | ||
| 151 | * <th id="byte2">Byte 2</th> | ||
| 152 | * <td> | ||
| 153 | * <table border="1" cellspacing="0" width="100%"> | ||
| 154 | * <tr> | ||
| 155 | * <td width="12%"><center>1</center> | ||
| 156 | * <td width="13%"><center>0</center> | ||
| 157 | * <td colspan="6"><center>bits 11-6</center> | ||
| 158 | * </tr> | ||
| 159 | * </table> | ||
| 160 | * </td> | ||
| 161 | * </tr> | ||
| 162 | * <tr> | ||
| 163 | * <th id="byte3">Byte 3</th> | ||
| 164 | * <td> | ||
| 165 | * <table border="1" cellspacing="0" width="100%"> | ||
| 166 | * <tr> | ||
| 167 | * <td width="12%"><center>1</center> | ||
| 168 | * <td width="13%"><center>0</center> | ||
| 169 | * <td colspan="6"><center>bits 5-0</center> | ||
| 170 | * </tr> | ||
| 171 | * </table> | ||
| 172 | * </td> | ||
| 173 | * </tr> | ||
| 174 | * </table> | ||
| 175 | * </blockquote> | ||
| 176 | * | ||
| 177 | * <p> | ||
| 178 | * The differences between this format and the | ||
| 179 | * standard UTF-8 format are the following: | ||
| 180 | * <ul> | ||
| 181 | * <li>The null byte <code>'\u0000'</code> is encoded in 2-byte format | ||
| 182 | * rather than 1-byte, so that the encoded strings never have | ||
| 183 | * embedded nulls. | ||
| 184 | * <li>Only the 1-byte, 2-byte, and 3-byte formats are used. | ||
| 185 | * <li><a href="../lang/Character.html#unicode">Supplementary characters</a> | ||
| 186 | * are represented in the form of surrogate pairs. | ||
| 187 | * </ul> | ||
| 188 | * @author Frank Yellin | ||
| 189 | * @see java.io.DataInputStream | ||
| 190 | * @see java.io.DataOutput | ||
| 191 | * @since JDK1.0 | ||
| 192 | */ | ||
| 193 | public | ||
| 194 | interface DataInput { | ||
| 195 | /** | ||
| 196 | * Reads some bytes from an input | ||
| 197 | * stream and stores them into the buffer | ||
| 198 | * array <code>b</code>. The number of bytes | ||
| 199 | * read is equal | ||
| 200 | * to the length of <code>b</code>. | ||
| 201 | * <p> | ||
| 202 | * This method blocks until one of the | ||
| 203 | * following conditions occurs:<p> | ||
| 204 | * <ul> | ||
| 205 | * <li><code>b.length</code> | ||
| 206 | * bytes of input data are available, in which | ||
| 207 | * case a normal return is made. | ||
| 208 | * | ||
| 209 | * <li>End of | ||
| 210 | * file is detected, in which case an <code>EOFException</code> | ||
| 211 | * is thrown. | ||
| 212 | * | ||
| 213 | * <li>An I/O error occurs, in | ||
| 214 | * which case an <code>IOException</code> other | ||
| 215 | * than <code>EOFException</code> is thrown. | ||
| 216 | * </ul> | ||
| 217 | * <p> | ||
| 218 | * If <code>b</code> is <code>null</code>, | ||
| 219 | * a <code>NullPointerException</code> is thrown. | ||
| 220 | * If <code>b.length</code> is zero, then | ||
| 221 | * no bytes are read. Otherwise, the first | ||
| 222 | * byte read is stored into element <code>b[0]</code>, | ||
| 223 | * the next one into <code>b[1]</code>, and | ||
| 224 | * so on. | ||
| 225 | * If an exception is thrown from | ||
| 226 | * this method, then it may be that some but | ||
| 227 | * not all bytes of <code>b</code> have been | ||
| 228 | * updated with data from the input stream. | ||
| 229 | * | ||
| 230 | * @param b the buffer into which the data is read. | ||
| 231 | * @exception EOFException if this stream reaches the end before reading | ||
| 232 | * all the bytes. | ||
| 233 | * @exception IOException if an I/O error occurs. | ||
| 234 | */ | ||
| 235 | void readFully(byte b[]) throws IOException; | ||
| 236 | |||
| 237 | /** | ||
| 238 | * | ||
| 239 | * Reads <code>len</code> | ||
| 240 | * bytes from | ||
| 241 | * an input stream. | ||
| 242 | * <p> | ||
| 243 | * This method | ||
| 244 | * blocks until one of the following conditions | ||
| 245 | * occurs:<p> | ||
| 246 | * <ul> | ||
| 247 | * <li><code>len</code> bytes | ||
| 248 | * of input data are available, in which case | ||
| 249 | * a normal return is made. | ||
| 250 | * | ||
| 251 | * <li>End of file | ||
| 252 | * is detected, in which case an <code>EOFException</code> | ||
| 253 | * is thrown. | ||
| 254 | * | ||
| 255 | * <li>An I/O error occurs, in | ||
| 256 | * which case an <code>IOException</code> other | ||
| 257 | * than <code>EOFException</code> is thrown. | ||
| 258 | * </ul> | ||
| 259 | * <p> | ||
| 260 | * If <code>b</code> is <code>null</code>, | ||
| 261 | * a <code>NullPointerException</code> is thrown. | ||
| 262 | * If <code>off</code> is negative, or <code>len</code> | ||
| 263 | * is negative, or <code>off+len</code> is | ||
| 264 | * greater than the length of the array <code>b</code>, | ||
| 265 | * then an <code>IndexOutOfBoundsException</code> | ||
| 266 | * is thrown. | ||
| 267 | * If <code>len</code> is zero, | ||
| 268 | * then no bytes are read. Otherwise, the first | ||
| 269 | * byte read is stored into element <code>b[off]</code>, | ||
| 270 | * the next one into <code>b[off+1]</code>, | ||
| 271 | * and so on. The number of bytes read is, | ||
| 272 | * at most, equal to <code>len</code>. | ||
| 273 | * | ||
| 274 | * @param b the buffer into which the data is read. | ||
| 275 | * @param off an int specifying the offset into the data. | ||
| 276 | * @param len an int specifying the number of bytes to read. | ||
| 277 | * @exception EOFException if this stream reaches the end before reading | ||
| 278 | * all the bytes. | ||
| 279 | * @exception IOException if an I/O error occurs. | ||
| 280 | */ | ||
| 281 | void readFully(byte b[], int off, int len) throws IOException; | ||
| 282 | |||
| 283 | /** | ||
| 284 | * Makes an attempt to skip over | ||
| 285 | * <code>n</code> bytes | ||
| 286 | * of data from the input | ||
| 287 | * stream, discarding the skipped bytes. However, | ||
| 288 | * it may skip | ||
| 289 | * over some smaller number of | ||
| 290 | * bytes, possibly zero. This may result from | ||
| 291 | * any of a | ||
| 292 | * number of conditions; reaching | ||
| 293 | * end of file before <code>n</code> bytes | ||
| 294 | * have been skipped is | ||
| 295 | * only one possibility. | ||
| 296 | * This method never throws an <code>EOFException</code>. | ||
| 297 | * The actual | ||
| 298 | * number of bytes skipped is returned. | ||
| 299 | * | ||
| 300 | * @param n the number of bytes to be skipped. | ||
| 301 | * @return the number of bytes actually skipped. | ||
| 302 | * @exception IOException if an I/O error occurs. | ||
| 303 | */ | ||
| 304 | int skipBytes(int n) throws IOException; | ||
| 305 | |||
| 306 | /** | ||
| 307 | * Reads one input byte and returns | ||
| 308 | * <code>true</code> if that byte is nonzero, | ||
| 309 | * <code>false</code> if that byte is zero. | ||
| 310 | * This method is suitable for reading | ||
| 311 | * the byte written by the <code>writeBoolean</code> | ||
| 312 | * method of interface <code>DataOutput</code>. | ||
| 313 | * | ||
| 314 | * @return the <code>boolean</code> value read. | ||
| 315 | * @exception EOFException if this stream reaches the end before reading | ||
| 316 | * all the bytes. | ||
| 317 | * @exception IOException if an I/O error occurs. | ||
| 318 | */ | ||
| 319 | boolean readBoolean() throws IOException; | ||
| 320 | |||
| 321 | /** | ||
| 322 | * Reads and returns one input byte. | ||
| 323 | * The byte is treated as a signed value in | ||
| 324 | * the range <code>-128</code> through <code>127</code>, | ||
| 325 | * inclusive. | ||
| 326 | * This method is suitable for | ||
| 327 | * reading the byte written by the <code>writeByte</code> | ||
| 328 | * method of interface <code>DataOutput</code>. | ||
| 329 | * | ||
| 330 | * @return the 8-bit value read. | ||
| 331 | * @exception EOFException if this stream reaches the end before reading | ||
| 332 | * all the bytes. | ||
| 333 | * @exception IOException if an I/O error occurs. | ||
| 334 | */ | ||
| 335 | byte readByte() throws IOException; | ||
| 336 | |||
| 337 | /** | ||
| 338 | * Reads one input byte, zero-extends | ||
| 339 | * it to type <code>int</code>, and returns | ||
| 340 | * the result, which is therefore in the range | ||
| 341 | * <code>0</code> | ||
| 342 | * through <code>255</code>. | ||
| 343 | * This method is suitable for reading | ||
| 344 | * the byte written by the <code>writeByte</code> | ||
| 345 | * method of interface <code>DataOutput</code> | ||
| 346 | * if the argument to <code>writeByte</code> | ||
| 347 | * was intended to be a value in the range | ||
| 348 | * <code>0</code> through <code>255</code>. | ||
| 349 | * | ||
| 350 | * @return the unsigned 8-bit value read. | ||
| 351 | * @exception EOFException if this stream reaches the end before reading | ||
| 352 | * all the bytes. | ||
| 353 | * @exception IOException if an I/O error occurs. | ||
| 354 | */ | ||
| 355 | int readUnsignedByte() throws IOException; | ||
| 356 | |||
| 357 | /** | ||
| 358 | * Reads two input bytes and returns | ||
| 359 | * a <code>short</code> value. Let <code>a</code> | ||
| 360 | * be the first byte read and <code>b</code> | ||
| 361 | * be the second byte. The value | ||
| 362 | * returned | ||
| 363 | * is: | ||
| 364 | * <p><pre><code>(short)((a << 8) | (b & 0xff)) | ||
| 365 | * </code></pre> | ||
| 366 | * This method | ||
| 367 | * is suitable for reading the bytes written | ||
| 368 | * by the <code>writeShort</code> method of | ||
| 369 | * interface <code>DataOutput</code>. | ||
| 370 | * | ||
| 371 | * @return the 16-bit value read. | ||
| 372 | * @exception EOFException if this stream reaches the end before reading | ||
| 373 | * all the bytes. | ||
| 374 | * @exception IOException if an I/O error occurs. | ||
| 375 | */ | ||
| 376 | short readShort() throws IOException; | ||
| 377 | |||
| 378 | /** | ||
| 379 | * Reads two input bytes and returns | ||
| 380 | * an <code>int</code> value in the range <code>0</code> | ||
| 381 | * through <code>65535</code>. Let <code>a</code> | ||
| 382 | * be the first byte read and | ||
| 383 | * <code>b</code> | ||
| 384 | * be the second byte. The value returned is: | ||
| 385 | * <p><pre><code>(((a & 0xff) << 8) | (b & 0xff)) | ||
| 386 | * </code></pre> | ||
| 387 | * This method is suitable for reading the bytes | ||
| 388 | * written by the <code>writeShort</code> method | ||
| 389 | * of interface <code>DataOutput</code> if | ||
| 390 | * the argument to <code>writeShort</code> | ||
| 391 | * was intended to be a value in the range | ||
| 392 | * <code>0</code> through <code>65535</code>. | ||
| 393 | * | ||
| 394 | * @return the unsigned 16-bit value read. | ||
| 395 | * @exception EOFException if this stream reaches the end before reading | ||
| 396 | * all the bytes. | ||
| 397 | * @exception IOException if an I/O error occurs. | ||
| 398 | */ | ||
| 399 | int readUnsignedShort() throws IOException; | ||
| 400 | |||
| 401 | /** | ||
| 402 | * Reads two input bytes and returns a <code>char</code> value. | ||
| 403 | * Let <code>a</code> | ||
| 404 | * be the first byte read and <code>b</code> | ||
| 405 | * be the second byte. The value | ||
| 406 | * returned is: | ||
| 407 | * <p><pre><code>(char)((a << 8) | (b & 0xff)) | ||
| 408 | * </code></pre> | ||
| 409 | * This method | ||
| 410 | * is suitable for reading bytes written by | ||
| 411 | * the <code>writeChar</code> method of interface | ||
| 412 | * <code>DataOutput</code>. | ||
| 413 | * | ||
| 414 | * @return the <code>char</code> value read. | ||
| 415 | * @exception EOFException if this stream reaches the end before reading | ||
| 416 | * all the bytes. | ||
| 417 | * @exception IOException if an I/O error occurs. | ||
| 418 | */ | ||
| 419 | char readChar() throws IOException; | ||
| 420 | |||
| 421 | /** | ||
| 422 | * Reads four input bytes and returns an | ||
| 423 | * <code>int</code> value. Let <code>a-d</code> | ||
| 424 | * be the first through fourth bytes read. The value returned is: | ||
| 425 | * <p><pre> | ||
| 426 | * <code> | ||
| 427 | * (((a & 0xff) << 24) | ((b & 0xff) << 16) | | ||
| 428 | *  ((c & 0xff) << 8) | (d & 0xff)) | ||
| 429 | * </code></pre> | ||
| 430 | * This method is suitable | ||
| 431 | * for reading bytes written by the <code>writeInt</code> | ||
| 432 | * method of interface <code>DataOutput</code>. | ||
| 433 | * | ||
| 434 | * @return the <code>int</code> value read. | ||
| 435 | * @exception EOFException if this stream reaches the end before reading | ||
| 436 | * all the bytes. | ||
| 437 | * @exception IOException if an I/O error occurs. | ||
| 438 | */ | ||
| 439 | int readInt() throws IOException; | ||
| 440 | |||
| 441 | /** | ||
| 442 | * Reads eight input bytes and returns | ||
| 443 | * a <code>long</code> value. Let <code>a-h</code> | ||
| 444 | * be the first through eighth bytes read. | ||
| 445 | * The value returned is: | ||
| 446 | * <p><pre> <code> | ||
| 447 | * (((long)(a & 0xff) << 56) | | ||
| 448 | * ((long)(b & 0xff) << 48) | | ||
| 449 | * ((long)(c & 0xff) << 40) | | ||
| 450 | * ((long)(d & 0xff) << 32) | | ||
| 451 | * ((long)(e & 0xff) << 24) | | ||
| 452 | * ((long)(f & 0xff) << 16) | | ||
| 453 | * ((long)(g & 0xff) << 8) | | ||
| 454 | * ((long)(h & 0xff))) | ||
| 455 | * </code></pre> | ||
| 456 | * <p> | ||
| 457 | * This method is suitable | ||
| 458 | * for reading bytes written by the <code>writeLong</code> | ||
| 459 | * method of interface <code>DataOutput</code>. | ||
| 460 | * | ||
| 461 | * @return the <code>long</code> value read. | ||
| 462 | * @exception EOFException if this stream reaches the end before reading | ||
| 463 | * all the bytes. | ||
| 464 | * @exception IOException if an I/O error occurs. | ||
| 465 | */ | ||
| 466 | long readLong() throws IOException; | ||
| 467 | |||
| 468 | /** | ||
| 469 | * Reads four input bytes and returns | ||
| 470 | * a <code>float</code> value. It does this | ||
| 471 | * by first constructing an <code>int</code> | ||
| 472 | * value in exactly the manner | ||
| 473 | * of the <code>readInt</code> | ||
| 474 | * method, then converting this <code>int</code> | ||
| 475 | * value to a <code>float</code> in | ||
| 476 | * exactly the manner of the method <code>Float.intBitsToFloat</code>. | ||
| 477 | * This method is suitable for reading | ||
| 478 | * bytes written by the <code>writeFloat</code> | ||
| 479 | * method of interface <code>DataOutput</code>. | ||
| 480 | * | ||
| 481 | * @return the <code>float</code> value read. | ||
| 482 | * @exception EOFException if this stream reaches the end before reading | ||
| 483 | * all the bytes. | ||
| 484 | * @exception IOException if an I/O error occurs. | ||
| 485 | */ | ||
| 486 | float readFloat() throws IOException; | ||
| 487 | |||
| 488 | /** | ||
| 489 | * Reads eight input bytes and returns | ||
| 490 | * a <code>double</code> value. It does this | ||
| 491 | * by first constructing a <code>long</code> | ||
| 492 | * value in exactly the manner | ||
| 493 | * of the <code>readlong</code> | ||
| 494 | * method, then converting this <code>long</code> | ||
| 495 | * value to a <code>double</code> in exactly | ||
| 496 | * the manner of the method <code>Double.longBitsToDouble</code>. | ||
| 497 | * This method is suitable for reading | ||
| 498 | * bytes written by the <code>writeDouble</code> | ||
| 499 | * method of interface <code>DataOutput</code>. | ||
| 500 | * | ||
| 501 | * @return the <code>double</code> value read. | ||
| 502 | * @exception EOFException if this stream reaches the end before reading | ||
| 503 | * all the bytes. | ||
| 504 | * @exception IOException if an I/O error occurs. | ||
| 505 | */ | ||
| 506 | double readDouble() throws IOException; | ||
| 507 | |||
| 508 | /** | ||
| 509 | * Reads the next line of text from the input stream. | ||
| 510 | * It reads successive bytes, converting | ||
| 511 | * each byte separately into a character, | ||
| 512 | * until it encounters a line terminator or | ||
| 513 | * end of | ||
| 514 | * file; the characters read are then | ||
| 515 | * returned as a <code>String</code>. Note | ||
| 516 | * that because this | ||
| 517 | * method processes bytes, | ||
| 518 | * it does not support input of the full Unicode | ||
| 519 | * character set. | ||
| 520 | * <p> | ||
| 521 | * If end of file is encountered | ||
| 522 | * before even one byte can be read, then <code>null</code> | ||
| 523 | * is returned. Otherwise, each byte that is | ||
| 524 | * read is converted to type <code>char</code> | ||
| 525 | * by zero-extension. If the character <code>'\n'</code> | ||
| 526 | * is encountered, it is discarded and reading | ||
| 527 | * ceases. If the character <code>'\r'</code> | ||
| 528 | * is encountered, it is discarded and, if | ||
| 529 | * the following byte converts  to the | ||
| 530 | * character <code>'\n'</code>, then that is | ||
| 531 | * discarded also; reading then ceases. If | ||
| 532 | * end of file is encountered before either | ||
| 533 | * of the characters <code>'\n'</code> and | ||
| 534 | * <code>'\r'</code> is encountered, reading | ||
| 535 | * ceases. Once reading has ceased, a <code>String</code> | ||
| 536 | * is returned that contains all the characters | ||
| 537 | * read and not discarded, taken in order. | ||
| 538 | * Note that every character in this string | ||
| 539 | * will have a value less than <code>\u0100</code>, | ||
| 540 | * that is, <code>(char)256</code>. | ||
| 541 | * | ||
| 542 | * @return the next line of text from the input stream, | ||
| 543 | * or <CODE>null</CODE> if the end of file is | ||
| 544 | * encountered before a byte can be read. | ||
| 545 | * @exception IOException if an I/O error occurs. | ||
| 546 | */ | ||
| 547 | String readLine() throws IOException; | ||
| 548 | |||
| 549 | /** | ||
| 550 | * Reads in a string that has been encoded using a | ||
| 551 | * <a href="#modified-utf-8">modified UTF-8</a> | ||
| 552 | * format. | ||
| 553 | * The general contract of <code>readUTF</code> | ||
| 554 | * is that it reads a representation of a Unicode | ||
| 555 | * character string encoded in modified | ||
| 556 | * UTF-8 format; this string of characters | ||
| 557 | * is then returned as a <code>String</code>. | ||
| 558 | * <p> | ||
| 559 | * First, two bytes are read and used to | ||
| 560 | * construct an unsigned 16-bit integer in | ||
| 561 | * exactly the manner of the <code>readUnsignedShort</code> | ||
| 562 | * method . This integer value is called the | ||
| 563 | * <i>UTF length</i> and specifies the number | ||
| 564 | * of additional bytes to be read. These bytes | ||
| 565 | * are then converted to characters by considering | ||
| 566 | * them in groups. The length of each group | ||
| 567 | * is computed from the value of the first | ||
| 568 | * byte of the group. The byte following a | ||
| 569 | * group, if any, is the first byte of the | ||
| 570 | * next group. | ||
| 571 | * <p> | ||
| 572 | * If the first byte of a group | ||
| 573 | * matches the bit pattern <code>0xxxxxxx</code> | ||
| 574 | * (where <code>x</code> means "may be <code>0</code> | ||
| 575 | * or <code>1</code>"), then the group consists | ||
| 576 | * of just that byte. The byte is zero-extended | ||
| 577 | * to form a character. | ||
| 578 | * <p> | ||
| 579 | * If the first byte | ||
| 580 | * of a group matches the bit pattern <code>110xxxxx</code>, | ||
| 581 | * then the group consists of that byte <code>a</code> | ||
| 582 | * and a second byte <code>b</code>. If there | ||
| 583 | * is no byte <code>b</code> (because byte | ||
| 584 | * <code>a</code> was the last of the bytes | ||
| 585 | * to be read), or if byte <code>b</code> does | ||
| 586 | * not match the bit pattern <code>10xxxxxx</code>, | ||
| 587 | * then a <code>UTFDataFormatException</code> | ||
| 588 | * is thrown. Otherwise, the group is converted | ||
| 589 | * to the character:<p> | ||
| 590 | * <pre><code>(char)(((a& 0x1F) << 6) | (b & 0x3F)) | ||
| 591 | * </code></pre> | ||
| 592 | * If the first byte of a group | ||
| 593 | * matches the bit pattern <code>1110xxxx</code>, | ||
| 594 | * then the group consists of that byte <code>a</code> | ||
| 595 | * and two more bytes <code>b</code> and <code>c</code>. | ||
| 596 | * If there is no byte <code>c</code> (because | ||
| 597 | * byte <code>a</code> was one of the last | ||
| 598 | * two of the bytes to be read), or either | ||
| 599 | * byte <code>b</code> or byte <code>c</code> | ||
| 600 | * does not match the bit pattern <code>10xxxxxx</code>, | ||
| 601 | * then a <code>UTFDataFormatException</code> | ||
| 602 | * is thrown. Otherwise, the group is converted | ||
| 603 | * to the character:<p> | ||
| 604 | * <pre><code> | ||
| 605 | * (char)(((a & 0x0F) << 12) | ((b & 0x3F) << 6) | (c & 0x3F)) | ||
| 606 | * </code></pre> | ||
| 607 | * If the first byte of a group matches the | ||
| 608 | * pattern <code>1111xxxx</code> or the pattern | ||
| 609 | * <code>10xxxxxx</code>, then a <code>UTFDataFormatException</code> | ||
| 610 | * is thrown. | ||
| 611 | * <p> | ||
| 612 | * If end of file is encountered | ||
| 613 | * at any time during this entire process, | ||
| 614 | * then an <code>EOFException</code> is thrown. | ||
| 615 | * <p> | ||
| 616 | * After every group has been converted to | ||
| 617 | * a character by this process, the characters | ||
| 618 | * are gathered, in the same order in which | ||
| 619 | * their corresponding groups were read from | ||
| 620 | * the input stream, to form a <code>String</code>, | ||
| 621 | * which is returned. | ||
| 622 | * <p> | ||
| 623 | * The <code>writeUTF</code> | ||
| 624 | * method of interface <code>DataOutput</code> | ||
| 625 | * may be used to write data that is suitable | ||
| 626 | * for reading by this method. | ||
| 627 | * @return a Unicode string. | ||
| 628 | * @exception EOFException if this stream reaches the end | ||
| 629 | * before reading all the bytes. | ||
| 630 | * @exception IOException if an I/O error occurs. | ||
| 631 | * @exception UTFDataFormatException if the bytes do not represent a | ||
| 632 | * valid modified UTF-8 encoding of a string. | ||
| 633 | */ | ||
| 634 | String readUTF() throws IOException; | ||
| 635 | } | ||