Source for java.io.File

   1: /* File.java -- Class representing a file on disk
   2:    Copyright (C) 1998, 1999, 2000, 2001, 2003, 2004, 2005
   3:    Free Software Foundation, Inc.
   4: 
   5: This file is part of GNU Classpath.
   6: 
   7: GNU Classpath is free software; you can redistribute it and/or modify
   8: it under the terms of the GNU General Public License as published by
   9: the Free Software Foundation; either version 2, or (at your option)
  10: any later version.
  11:  
  12: GNU Classpath is distributed in the hope that it will be useful, but
  13: WITHOUT ANY WARRANTY; without even the implied warranty of
  14: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15: General Public License for more details.
  16: 
  17: You should have received a copy of the GNU General Public License
  18: along with GNU Classpath; see the file COPYING.  If not, write to the
  19: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  20: 02110-1301 USA.
  21: 
  22: Linking this library statically or dynamically with other modules is
  23: making a combined work based on this library.  Thus, the terms and
  24: conditions of the GNU General Public License cover the whole
  25: combination.
  26: 
  27: As a special exception, the copyright holders of this library give you
  28: permission to link this library with independent modules to produce an
  29: executable, regardless of the license terms of these independent
  30: modules, and to copy and distribute the resulting executable under
  31: terms of your choice, provided that you also meet, for each linked
  32: independent module, the terms and conditions of the license of that
  33: module.  An independent module is a module which is not derived from
  34: or based on this library.  If you modify this library, you may extend
  35: this exception to your version of the library, but you are not
  36: obligated to do so.  If you do not wish to do so, delete this
  37: exception statement from your version. */
  38: 
  39: 
  40: package java.io;
  41: 
  42: import gnu.classpath.SystemProperties;
  43: 
  44: import java.net.MalformedURLException;
  45: import java.net.URI;
  46: import java.net.URISyntaxException;
  47: import java.net.URL;
  48: 
  49: /* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
  50:  * "The Java Language Specification", ISBN 0-201-63451-1
  51:  * Status:  Complete to version 1.3.
  52:  */
  53: 
  54: /**
  55:  * This class represents a file or directory on a local disk.  It provides
  56:  * facilities for dealing with a variety of systems that use various
  57:  * types of path separators ("/" versus "\", for example).  It also
  58:  * contains method useful for creating and deleting files and directories.
  59:  *
  60:  * @author Aaron M. Renn (arenn@urbanophile.com)
  61:  * @author Tom Tromey (tromey@cygnus.com)
  62:  */
  63: public class File implements Serializable, Comparable
  64: {
  65:   private static final long serialVersionUID = 301077366599181567L;
  66: 
  67:   /**
  68:    * This is the path separator string for the current host. This field
  69:    * contains the value of the <code>file.separator</code> system property.
  70:    * An example separator string would be "/" on the GNU system.
  71:    */
  72:   public static final String separator = SystemProperties.getProperty("file.separator");
  73:   private static final String dupSeparator = separator + separator;
  74: 
  75:   /**
  76:    * This is the first character of the file separator string.  On many
  77:    * hosts (for example, on the GNU system), this represents the entire 
  78:    * separator string.  The complete separator string is obtained from the
  79:    * <code>file.separator</code>system property.
  80:    */
  81:   public static final char separatorChar = separator.charAt(0);
  82:   
  83:   /**
  84:    * This is the string that is used to separate the host name from the
  85:    * path name in paths than include the host name.  It is the value of
  86:    * the <code>path.separator</code> system property.
  87:    */
  88:   public static final String pathSeparator
  89:     = SystemProperties.getProperty("path.separator");
  90:   
  91:   /**
  92:    * This is the first character of the string used to separate the host name
  93:    * from the path name in paths that include a host.  The separator string
  94:    * is taken from the <code>path.separator</code> system property.
  95:    */
  96:   public static final char pathSeparatorChar = pathSeparator.charAt(0);
  97: 
  98:   /**
  99:    * This is the path to the file set when the object is created.  It
 100:    * may be an absolute or relative path name.
 101:    */
 102:   private String path;
 103:   
 104:   
 105:   /**
 106:    * The time (millisecond), when the last temporary file was created.
 107:    */
 108:   private static long last_tmp;
 109:   
 110:   /**
 111:    * The number of files, created during the current millisecond.
 112:    */
 113:   private static int n_created;  
 114: 
 115:   /**
 116:    * This method tests whether or not the current thread is allowed to
 117:    * to read the file pointed to by this object.  This will be true if and
 118:    * and only if 1) the file exists and 2) the <code>SecurityManager</code>
 119:    * (if any) allows access to the file via it's <code>checkRead</code>
 120:    * method 3) the file is readable.
 121:    *
 122:    * @return <code>true</code> if reading is allowed, 
 123:    * <code>false</code> otherwise
 124:    *
 125:    * @exception SecurityException If the <code>SecurityManager</code> 
 126:    * does not allow access to the file
 127:    */
 128:   public boolean canRead()
 129:   {
 130:     // Test for existence. This also does the SecurityManager check
 131:     if (!exists())
 132:       return false;
 133: 
 134:     return VMFile.canRead(path);
 135:   }
 136: 
 137:   /**
 138:    * This method test whether or not the current thread is allowed to
 139:    * write to this object.  This will be true if and only if 1) The
 140:    * <code>SecurityManager</code> (if any) allows write access to the
 141:    * file and 2) The file exists and 3) The file is writable.  To determine
 142:    * whether or not a non-existent file can be created, check the parent
 143:    * directory for write access.
 144:    *
 145:    * @return <code>true</code> if writing is allowed, <code>false</code> 
 146:    * otherwise
 147:    *
 148:    * @exception SecurityException If the <code>SecurityManager</code> 
 149:    * does not allow access to the file
 150:    */
 151:   public boolean canWrite()
 152:   {
 153:     // First do a SecurityCheck before doing anything else.
 154:     checkWrite();
 155:      
 156:     // Test for existence.  This is required by the spec
 157:     if (! VMFile.exists(path))
 158:       return false;
 159: 
 160:     if (VMFile.isDirectory(path))
 161:       return VMFile.canWriteDirectory(this);
 162:     else
 163:       return VMFile.canWrite(path);
 164:   }
 165: 
 166:   /**
 167:    * This method creates a new file of zero length with the same name as
 168:    * the path of this <code>File</code> object if an only if that file
 169:    * does not already exist.
 170:    * <p>
 171:    * A <code>SecurityManager.checkWrite</code> check is done prior
 172:    * to performing this action.
 173:    *
 174:    * @return <code>true</code> if the file was created, <code>false</code> if
 175:    * the file alread existed.
 176:    *
 177:    * @exception IOException If an I/O error occurs
 178:    * @exception SecurityException If the <code>SecurityManager</code> will
 179:    * not allow this operation to be performed.
 180:    *
 181:    * @since 1.2
 182:    */
 183:   public boolean createNewFile() throws IOException
 184:   {
 185:     checkWrite();
 186:     return VMFile.create(path);
 187:   }
 188:   /**
 189:    * This method deletes the file represented by this object.  If this file
 190:    * is a directory, it must be empty in order for the delete to succeed.
 191:    *
 192:    * @return <code>true</code> if the file was deleted, <code>false</code> 
 193:    * otherwise
 194:    *
 195:    * @exception SecurityException If deleting of the file is not allowed
 196:    */
 197:   public synchronized boolean delete()
 198:   {
 199:     SecurityManager s = System.getSecurityManager();
 200:     
 201:     if (s != null)
 202:       s.checkDelete(path);
 203:     
 204:     return VMFile.delete(path);
 205:   }
 206: 
 207:   /**
 208:    * This method tests two <code>File</code> objects for equality by 
 209:    * comparing the path of the specified <code>File</code> against the path
 210:    * of this object.  The two objects are equal if an only if 1) The
 211:    * argument is not null 2) The argument is a <code>File</code> object and
 212:    * 3) The path of the <code>File</code>argument is equal to the path
 213:    * of this object.
 214:    * <p>
 215:    * The paths of the files are determined by calling the 
 216:    * <code>getPath()</code>
 217:    * method on each object.
 218:    *
 219:    * @return <code>true</code> if the two objects are equal, 
 220:    * <code>false</code> otherwise.
 221:    */
 222:   public boolean equals(Object obj)
 223:   {
 224:     if (! (obj instanceof File))
 225:       return false;
 226:     
 227:     File other = (File) obj;
 228: 
 229:     if (VMFile.IS_CASE_SENSITIVE)
 230:       return path.equals(other.path);
 231:     else
 232:       return path.equalsIgnoreCase(other.path);
 233:   }
 234: 
 235:   /**
 236:    * This method tests whether or not the file represented by the object
 237:    * actually exists on the filesystem.
 238:    *
 239:    * @return <code>true</code> if the file exists, <code>false</code>otherwise.
 240:    *
 241:    * @exception SecurityException If reading of the file is not permitted
 242:    */
 243:   public boolean exists()
 244:   {
 245:     checkRead();
 246:     return VMFile.exists(path);
 247:   }
 248: 
 249:   /**
 250:    * This method initializes a new <code>File</code> object to represent
 251:    * a file with the specified path.
 252:    *
 253:    * @param name The path name of the file
 254:    */
 255:   public File(String name)
 256:   {
 257:     path = normalizePath (name);
 258:   }
 259:  
 260:   // Remove duplicate and redundant separator characters.
 261:   private String normalizePath(String p)
 262:   {
 263:     // On Windows, convert any '/' to '\'.  This appears to be the same logic
 264:     // that Sun's Win32 Java performs.
 265:     if (separatorChar == '\\')
 266:       {
 267:         p = p.replace ('/', '\\');
 268:     // We have to special case the "\c:" prefix.
 269:     if (p.length() > 2 && p.charAt(0) == '\\' &&
 270:         ((p.charAt(1) >= 'a' && p.charAt(1) <= 'z') ||
 271:         (p.charAt(1) >= 'A' && p.charAt(1) <= 'Z')) &&
 272:         p.charAt(2) == ':')
 273:       p = p.substring(1);
 274:       }
 275: 
 276:     int dupIndex = p.indexOf(dupSeparator);
 277:     int plen = p.length();
 278: 
 279:     // Special case: permit Windows UNC path prefix.
 280:     if (dupSeparator.equals("\\\\") && dupIndex == 0)
 281:       dupIndex = p.indexOf(dupSeparator, 1);
 282: 
 283:     if (dupIndex == -1)
 284:       {
 285:         // Ignore trailing separator (though on Windows "a:\", for
 286:         // example, is a valid and minimal path).
 287:         if (plen > 1 && p.charAt (plen - 1) == separatorChar)
 288:       {
 289:         if (! (separatorChar == '\\' && plen == 3 && p.charAt (1) == ':'))
 290:           return p.substring (0, plen - 1);
 291:       }
 292:     else
 293:       return p;
 294:       }
 295:     
 296:     StringBuffer newpath = new StringBuffer(plen);
 297:     int last = 0;
 298:     while (dupIndex != -1)
 299:       {
 300:         newpath.append(p.substring(last, dupIndex));
 301:     // Ignore the duplicate path characters.
 302:     while (p.charAt(dupIndex) == separatorChar)
 303:       {
 304:         dupIndex++;
 305:         if (dupIndex == plen)
 306:           return newpath.toString();
 307:       }
 308:     newpath.append(separatorChar);
 309:     last = dupIndex;
 310:     dupIndex = p.indexOf(dupSeparator, last);
 311:       }
 312:     
 313:     // Again, ignore possible trailing separator (except special cases
 314:     // like "a:\" on Windows).
 315:     int end;
 316:     if (plen > 1 && p.charAt (plen - 1) == separatorChar)
 317:     {
 318:       if (separatorChar == '\\' && plen == 3 && p.charAt (1) == ':')
 319:         end = plen;
 320:       else
 321:         end = plen - 1;
 322:     }
 323:     else
 324:       end = plen;
 325:     newpath.append(p.substring(last, end));
 326:     
 327:     return newpath.toString();
 328:   }
 329:  
 330:   /**
 331:    * This method initializes a new <code>File</code> object to represent
 332:    * a file in the specified named directory.  The path name to the file
 333:    * will be the directory name plus the separator string plus the file
 334:    * name.  If the directory path name ends in the separator string, another
 335:    * separator string will still be appended.
 336:    *
 337:    * @param dirPath The path to the directory the file resides in
 338:    * @param name The name of the file
 339:    */
 340:   public File(String dirPath, String name)
 341:   {
 342:     if (name == null)
 343:       throw new NullPointerException();
 344:     if (dirPath != null)
 345:       {
 346:     if (dirPath.length() > 0)
 347:       {
 348:         // Try to be smart about the number of separator characters.
 349:         if (dirPath.charAt(dirPath.length() - 1) == separatorChar
 350:         || name.length() == 0)
 351:           path = normalizePath(dirPath + name);
 352:         else
 353:           path = normalizePath(dirPath + separatorChar + name);
 354:       }
 355:     else
 356:       {
 357:         // If dirPath is empty, use a system dependant
 358:         // default prefix.
 359:         // Note that the leading separators in name have
 360:         // to be chopped off, to prevent them forming
 361:         // a UNC prefix on Windows.
 362:         if (separatorChar == '\\' /* TODO use ON_WINDOWS */)
 363:           {
 364:         int skip = 0;
 365:         while(name.length() > skip
 366:             && (name.charAt(skip) == separatorChar
 367:             || name.charAt(skip) == '/'))
 368:           {
 369:             skip++;
 370:           }
 371:         name = name.substring(skip);
 372:           }
 373:         path = normalizePath(separatorChar + name);
 374:       }
 375:       }
 376:     else
 377:       path = normalizePath(name);
 378:   }
 379: 
 380:   /**
 381:    * This method initializes a new <code>File</code> object to represent
 382:    * a file in the specified directory.  If the <code>directory</code>
 383:    * argument is <code>null</code>, the file is assumed to be in the
 384:    * current directory as specified by the <code>user.dir</code> system
 385:    * property
 386:    *
 387:    * @param directory The directory this file resides in
 388:    * @param name The name of the file
 389:    */
 390:   public File(File directory, String name)
 391:   {
 392:     this (directory == null ? null : directory.path, name);
 393:   }
 394: 
 395:   /**
 396:    * This method initializes a new <code>File</code> object to represent
 397:    * a file corresponding to the specified <code>file:</code> protocol URI.
 398:    *
 399:    * @param uri The uri.
 400:    */
 401:   public File(URI uri)
 402:   {
 403:     if (uri == null)
 404:     throw new NullPointerException("uri is null");
 405: 
 406:     if (!uri.getScheme().equals("file"))
 407:     throw new IllegalArgumentException("invalid uri protocol");
 408: 
 409:     path = normalizePath(uri.getPath());
 410:   }
 411: 
 412:   /**
 413:    * This method returns the path of this file as an absolute path name.
 414:    * If the path name is already absolute, then it is returned.  Otherwise
 415:    * the value returned is the current directory plus the separatory
 416:    * string plus the path of the file.  The current directory is determined
 417:    * from the <code>user.dir</code> system property.
 418:    *
 419:    * @return The absolute path of this file
 420:    */
 421:   public String getAbsolutePath()
 422:   {
 423:     if (isAbsolute())
 424:       return path;
 425:     else if (separatorChar == '\\' 
 426:              && path.length() > 0 && path.charAt (0) == '\\')
 427:       {
 428:         // On Windows, even if the path starts with a '\\' it is not
 429:         // really absolute until we prefix the drive specifier from
 430:         // the current working directory to it.
 431:         return System.getProperty ("user.dir").substring (0, 2) + path;
 432:       }
 433:     else if (separatorChar == '\\' 
 434:              && path.length() > 1 && path.charAt (1) == ':'
 435:              && ((path.charAt (0) >= 'a' && path.charAt (0) <= 'z')
 436:                  || (path.charAt (0) >= 'A' && path.charAt (0) <= 'Z')))
 437:       {
 438:         // On Windows, a process has a current working directory for
 439:         // each drive and a path like "G:foo\bar" would mean the 
 440:         // absolute path "G:\wombat\foo\bar" if "\wombat" is the 
 441:         // working directory on the G drive.
 442:         String drvDir = null;
 443:         try
 444:           {
 445:             drvDir = new File (path.substring (0, 2)).getCanonicalPath();
 446:           }
 447:         catch (IOException e)
 448:           {
 449:             drvDir = path.substring (0, 2) + "\\";
 450:           }
 451:         
 452:         // Note: this would return "C:\\." for the path "C:.", if "\"
 453:         // is the working folder on the C drive, but this is 
 454:         // consistent with what Sun's JRE 1.4.1.01 actually returns!
 455:         if (path.length() > 2)
 456:           return drvDir + '\\' + path.substring (2, path.length());
 457:         else
 458:           return drvDir;
 459:       }
 460:     else
 461:       return System.getProperty ("user.dir") + separatorChar + path;
 462:   }
 463: 
 464:   /**
 465:    * This method returns a <code>File</code> object representing the
 466:    * absolute path of this object.
 467:    *
 468:    * @return A <code>File</code> with the absolute path of the object.
 469:    *
 470:    * @since 1.2
 471:    */
 472:   public File getAbsoluteFile()
 473:   {
 474:     return new File(getAbsolutePath());
 475:   }
 476: 
 477:   /**
 478:    * This method returns a canonical representation of the pathname of
 479:    * this file.  The actual form of the canonical representation is
 480:    * different.  On the GNU system, the canonical form differs from the
 481:    * absolute form in that all relative file references to "." and ".."
 482:    * are resolved and removed.
 483:    * <p>
 484:    * Note that this method, unlike the other methods which return path
 485:    * names, can throw an IOException.  This is because native method 
 486:    * might be required in order to resolve the canonical path
 487:    *
 488:    * @exception IOException If an error occurs
 489:    */
 490:   public String getCanonicalPath() throws IOException
 491:   {
 492:     // On Windows, getAbsolutePath might end up calling us, so we
 493:     // have to special case that call to avoid infinite recursion.
 494:     if (separatorChar == '\\' && path.length() == 2 &&
 495:     ((path.charAt(0) >= 'a' && path.charAt(0) <= 'z') ||
 496:      (path.charAt(0) >= 'A' && path.charAt(0) <= 'Z')) &&
 497:     path.charAt(1) == ':')
 498:     {
 499:     return VMFile.toCanonicalForm(path);
 500:     }
 501:     // Call getAbsolutePath first to make sure that we do the
 502:     // current directory handling, because the native code
 503:     // may have a different idea of the current directory.
 504:     return VMFile.toCanonicalForm(getAbsolutePath());
 505:   }
 506: 
 507:   /**
 508:    * This method returns a <code>File</code> object representing the
 509:    * canonical path of this object.
 510:    *
 511:    * @return A <code>File</code> instance representing the canonical path of
 512:    * this object.
 513:    *
 514:    * @exception IOException If an error occurs.
 515:    *
 516:    * @since 1.2
 517:    */
 518:   public File getCanonicalFile() throws IOException
 519:   {
 520:     return new File(getCanonicalPath());
 521:   }
 522: 
 523:   /**
 524:    * This method returns the name of the file.  This is everything in the
 525:    * complete path of the file after the last instance of the separator
 526:    * string.
 527:    *
 528:    * @return The file name
 529:    */
 530:   public String getName()
 531:   {
 532:       return VMFile.getName(path);
 533:   }
 534: 
 535:   /**
 536:    * This method returns a <code>String</code> the represents this file's
 537:    * parent.  <code>null</code> is returned if the file has no parent.  The
 538:    * parent is determined via a simple operation which removes the
 539:    *
 540:    * @return The parent directory of this file
 541:    */
 542:   public String getParent()
 543:   {
 544:     String prefix = null;
 545:     int nameSeqIndex = 0;
 546: 
 547:     // The "prefix", if present, is the leading "/" on UNIX and 
 548:     // either the drive specifier (e.g. "C:") or the leading "\\"
 549:     // of a UNC network path on Windows.
 550:     if (separatorChar == '/' && path.charAt (0) == '/')
 551:       {
 552:         prefix = "/";
 553:         nameSeqIndex = 1;
 554:       }
 555:     else if (separatorChar == '\\' && path.length() > 1)
 556:       {
 557:         if ((path.charAt (0) == '\\' && path.charAt (1) == '\\')
 558:             || (((path.charAt (0) >= 'a' && path.charAt (0) <= 'z')
 559:                  || (path.charAt (0) >= 'A' && path.charAt (0) <= 'Z'))
 560:                 && path.charAt (1) == ':'))
 561:           {
 562:             prefix = path.substring (0, 2);
 563:             nameSeqIndex = 2;
 564:           }
 565:       }
 566: 
 567:     // According to the JDK docs, the returned parent path is the 
 568:     // portion of the name sequence before the last separator
 569:     // character, if found, prefixed by the prefix, otherwise null.
 570:     if (nameSeqIndex < path.length())
 571:       {
 572:         String nameSeq = path.substring (nameSeqIndex, path.length());
 573:         int last = nameSeq.lastIndexOf (separatorChar);
 574:         if (last == -1)
 575:           return prefix;
 576:         else if (last == (nameSeq.length() - 1))
 577:           // Note: The path would not have a trailing separator
 578:           // except for cases like "C:\" on Windows (see 
 579:           // normalizePath( )), where Sun's JRE 1.4 returns null.
 580:           return null;
 581:         else if (last == 0)
 582:           last++;
 583: 
 584:         if (prefix != null)
 585:           return prefix + nameSeq.substring (0, last);
 586:         else
 587:           return nameSeq.substring (0, last);
 588:       }
 589:     else
 590:       // Sun's JRE 1.4 returns null if the prefix is the only 
 591:       // component of the path - so "/" gives null on UNIX and 
 592:       // "C:", "\\", etc. return null on Windows.
 593:       return null;
 594:   }
 595: 
 596:   /**
 597:    * This method returns a <code>File</code> object representing the parent
 598:    * file of this one.
 599:    *
 600:    * @return a <code>File</code> for the parent of this object.  
 601:    * <code>null</code>
 602:    * will be returned if this object does not have a parent.
 603:    *
 604:    * @since 1.2
 605:    */
 606:   public File getParentFile()
 607:   {
 608:     String parent = getParent();
 609:     return parent != null ? new File(parent) : null;
 610:   }
 611: 
 612:   /**
 613:    * Returns the path name that represents this file.  May be a relative
 614:    * or an absolute path name
 615:    *
 616:    * @return The pathname of this file
 617:    */
 618:   public String getPath()
 619:   {
 620:     return path;
 621:   }
 622: 
 623:   /**
 624:    * This method returns a hash code representing this file.  It is the
 625:    * hash code of the path of this file (as returned by <code>getPath()</code>)
 626:    * exclusived or-ed with the value 1234321.
 627:    *
 628:    * @return The hash code for this object
 629:    */
 630:   public int hashCode()
 631:   {
 632:     if (VMFile.IS_CASE_SENSITIVE)
 633:       return path.hashCode() ^ 1234321;
 634:     else
 635:       return path.toLowerCase().hashCode() ^ 1234321;
 636:   }
 637: 
 638:   /**
 639:    * This method returns true if this object represents an absolute file
 640:    * path and false if it does not.  The definition of an absolute path varies
 641:    * by system.  As an example, on GNU systems, a path is absolute if it starts
 642:    * with a "/".
 643:    *
 644:    * @return <code>true</code> if this object represents an absolute 
 645:    * file name, <code>false</code> otherwise.
 646:    */
 647:   public boolean isAbsolute()
 648:   {
 649:     if (separatorChar == '\\')
 650:     return path.startsWith(dupSeparator) || 
 651:         (path.length() > 2 && 
 652:          ((path.charAt(0) >= 'a' && path.charAt(0) <= 'z') ||
 653:           (path.charAt(0) >= 'A' && path.charAt(0) <= 'Z')) &&
 654:          path.charAt(1) == ':' &&
 655:          path.charAt(2) == '\\');
 656:     else
 657:     return path.startsWith(separator);
 658:   }
 659: 
 660:   /**
 661:    * This method tests whether or not the file represented by this object
 662:    * is a directory.  In order for this method to return <code>true</code>,
 663:    * the file represented by this object must exist and be a directory.
 664:    * 
 665:    * @return <code>true</code> if this file is a directory, <code>false</code>
 666:    * otherwise
 667:    *
 668:    * @exception SecurityException If reading of the file is not permitted
 669:    */
 670:   public boolean isDirectory()
 671:   {
 672:     checkRead();
 673:     return VMFile.isDirectory(path); 
 674:   }
 675: 
 676:   /**
 677:    * This method tests whether or not the file represented by this object
 678:    * is a "plain" file.  A file is a plain file if and only if it 1) Exists,
 679:    * 2) Is not a directory or other type of special file.
 680:    *
 681:    * @return <code>true</code> if this is a plain file, <code>false</code> 
 682:    * otherwise
 683:    *
 684:    * @exception SecurityException If reading of the file is not permitted
 685:    */
 686:   public boolean isFile()
 687:   {
 688:     checkRead();
 689:     return VMFile.isFile(path);
 690:   }
 691: 
 692:   /**
 693:    * This method tests whether or not this file represents a "hidden" file.
 694:    * On GNU systems, a file is hidden if its name begins with a "."
 695:    * character.  Files with these names are traditionally not shown with
 696:    * directory listing tools.
 697:    *
 698:    * @return <code>true</code> if the file is hidden, <code>false</code>
 699:    * otherwise.
 700:    *
 701:    * @since 1.2
 702:    */
 703:   public boolean isHidden()
 704:   {
 705:     return VMFile.isHidden(path);
 706:   }
 707: 
 708:   /**
 709:    * This method returns the last modification time of this file.  The
 710:    * time value returned is an abstract value that should not be interpreted
 711:    * as a specified time value.  It is only useful for comparing to other
 712:    * such time values returned on the same system.  In that case, the larger
 713:    * value indicates a more recent modification time. 
 714:    * <p>
 715:    * If the file does not exist, then a value of 0 is returned.
 716:    *
 717:    * @return The last modification time of the file
 718:    *
 719:    * @exception SecurityException If reading of the file is not permitted
 720:    */
 721:   public long lastModified()
 722:   {
 723:     checkRead();
 724:     return VMFile.lastModified(path);
 725:   }
 726: 
 727:   /**
 728:    * This method returns the length of the file represented by this object,
 729:    * or 0 if the specified file does not exist.
 730:    *
 731:    * @return The length of the file
 732:    *
 733:    * @exception SecurityException If reading of the file is not permitted
 734:    */
 735:   public long length()
 736:   {
 737:     checkRead();
 738:     return VMFile.length(path);
 739:   }
 740: 
 741:   /**
 742:    * This method returns a array of <code>String</code>'s representing the
 743:    * list of files is then directory represented by this object.  If this
 744:    * object represents a non-directory file or a non-existent file, then
 745:    * <code>null</code> is returned.  The list of files will not contain
 746:    * any names such as "." or ".." which indicate the current or parent
 747:    * directory.  Also, the names are not guaranteed to be sorted.
 748:    * <p>
 749:    * In this form of the <code>list()</code> method, a filter is specified
 750:    * that allows the caller to control which files are returned in the
 751:    * list.  The <code>FilenameFilter</code> specified is called for each
 752:    * file returned to determine whether or not that file should be included
 753:    * in the list.
 754:    * <p>
 755:    * A <code>SecurityManager</code> check is made prior to reading the
 756:    * directory.  If read access to the directory is denied, an exception
 757:    * will be thrown.
 758:    *
 759:    * @param filter An object which will identify files to exclude from 
 760:    * the directory listing.
 761:    *
 762:    * @return An array of files in the directory, or <code>null</code> 
 763:    * if this object does not represent a valid directory.
 764:    * 
 765:    * @exception SecurityException If read access is not allowed to the 
 766:    * directory by the <code>SecurityManager</code>
 767:    */
 768:   public String[] list(FilenameFilter filter)
 769:   {
 770:     checkRead();
 771: 
 772:     if (!exists() || !isDirectory())
 773:       return null;
 774:     
 775:     // Get the list of files
 776:     String files[] = VMFile.list(path);
 777:     
 778:     // Check if an error occured in listInternal().
 779:     if (files == null)
 780:       return null;
 781: 
 782:     if (filter == null)
 783:       return files;
 784:     
 785:     // Apply the filter
 786:     int count = 0;
 787:     for (int i = 0; i < files.length; i++)
 788:       {
 789:         if (filter.accept(this, files[i]))
 790:         ++count;
 791:         else
 792:         files[i] = null;
 793:       }
 794: 
 795:     String[] retfiles = new String[count];
 796:     count = 0;
 797:     for (int i = 0; i < files.length; i++)
 798:       if (files[i] != null)
 799:         retfiles[count++] = files[i];
 800: 
 801:     return retfiles;
 802:   }
 803: 
 804:   /**
 805:    * This method returns a array of <code>String</code>'s representing the
 806:    * list of files is then directory represented by this object.  If this
 807:    * object represents a non-directory file or a non-existent file, then
 808:    * <code>null</code> is returned.  The list of files will not contain
 809:    * any names such as "." or ".." which indicate the current or parent
 810:    * directory.  Also, the names are not guaranteed to be sorted.
 811:    * <p>
 812:    * A <code>SecurityManager</code> check is made prior to reading the
 813:    * directory.  If read access to the directory is denied, an exception
 814:    * will be thrown.
 815:    *
 816:    * @return An array of files in the directory, or <code>null</code> if 
 817:    * this object does not represent a valid directory.
 818:    * 
 819:    * @exception SecurityException If read access is not allowed to the 
 820:    * directory by the <code>SecurityManager</code>
 821:    */
 822:   public String[] list()
 823:   {
 824:     return list(null);
 825:   }
 826: 
 827:   /**
 828:    * This method returns an array of <code>File</code> objects representing
 829:    * all the files in the directory represented by this object. If this
 830:    * object does not represent a directory, <code>null</code> is returned.
 831:    * Each of the returned <code>File</code> object is constructed with this
 832:    * object as its parent.
 833:    * <p>
 834:    * A <code>SecurityManager</code> check is made prior to reading the
 835:    * directory.  If read access to the directory is denied, an exception
 836:    * will be thrown.
 837:    *
 838:    * @return An array of <code>File</code> objects for this directory.
 839:    *
 840:    * @exception SecurityException If the <code>SecurityManager</code> denies
 841:    * access to this directory.
 842:    *
 843:    * @since 1.2
 844:    */
 845:   public File[] listFiles()
 846:   {
 847:     return listFiles((FilenameFilter) null);
 848:   }
 849:   
 850:   /**
 851:    * This method returns an array of <code>File</code> objects representing
 852:    * all the files in the directory represented by this object. If this
 853:    * object does not represent a directory, <code>null</code> is returned.
 854:    * Each of the returned <code>File</code> object is constructed with this
 855:    * object as its parent.
 856:    * <p> 
 857:    * In this form of the <code>listFiles()</code> method, a filter is specified
 858:    * that allows the caller to control which files are returned in the
 859:    * list.  The <code>FilenameFilter</code> specified is called for each
 860:    * file returned to determine whether or not that file should be included
 861:    * in the list.
 862:    * <p>
 863:    * A <code>SecurityManager</code> check is made prior to reading the
 864:    * directory.  If read access to the directory is denied, an exception
 865:    * will be thrown.
 866:    *
 867:    * @return An array of <code>File</code> objects for this directory.
 868:    *
 869:    * @exception SecurityException If the <code>SecurityManager</code> denies
 870:    * access to this directory.
 871:    *
 872:    * @since 1.2
 873:    */
 874:   public File[] listFiles(FilenameFilter filter)
 875:   {
 876:     String[] filelist = list(filter);
 877:     
 878:     if (filelist == null)
 879:       return null;
 880: 
 881:     File[] fobjlist = new File [filelist.length];
 882: 
 883:     for (int i = 0; i < filelist.length; i++)
 884:       fobjlist [i] = new File(this, filelist [i]);
 885: 
 886:     return fobjlist;
 887:   }
 888: 
 889:   /**
 890:    * This method returns an array of <code>File</code> objects representing
 891:    * all the files in the directory represented by this object. If this
 892:    * object does not represent a directory, <code>null</code> is returned.
 893:    * Each of the returned <code>File</code> object is constructed with this
 894:    * object as its parent.
 895:    * <p> 
 896:    * In this form of the <code>listFiles()</code> method, a filter is specified
 897:    * that allows the caller to control which files are returned in the
 898:    * list.  The <code>FileFilter</code> specified is called for each
 899:    * file returned to determine whether or not that file should be included
 900:    * in the list.
 901:    * <p>
 902:    * A <code>SecurityManager</code> check is made prior to reading the
 903:    * directory.  If read access to the directory is denied, an exception
 904:    * will be thrown.
 905:    *
 906:    * @return An array of <code>File</code> objects for this directory.
 907:    *
 908:    * @exception SecurityException If the <code>SecurityManager</code> denies
 909:    * access to this directory.
 910:    *
 911:    * @since 1.2
 912:    */
 913:   public File[] listFiles(FileFilter filter)
 914:   {
 915:     File[] fobjlist = listFiles((FilenameFilter) null);
 916: 
 917:     if (fobjlist == null)
 918:       return null;
 919: 
 920:     if (filter == null)
 921:       return fobjlist;
 922: 
 923:     int count = 0;
 924:     for (int i = 0; i < fobjlist.length; i++)
 925:       if (filter.accept(fobjlist[i]) == true)
 926:         ++count;
 927: 
 928:     File[] final_list = new File[count];
 929:     count = 0;
 930:     for (int i = 0; i < fobjlist.length; i++)
 931:       if (filter.accept(fobjlist[i]) == true)
 932:         {
 933:           final_list[count] = fobjlist[i];
 934:           ++count;
 935:         }
 936: 
 937:     return final_list;
 938:   }
 939: 
 940:   /**
 941:    * This method returns a <code>String</code> that is the path name of the
 942:    * file as returned by <code>getPath</code>.
 943:    *
 944:    * @return A <code>String</code> representation of this file
 945:    */
 946:   public String toString()
 947:   {
 948:     return path;
 949:   }
 950: 
 951:   /**
 952:    * @return A <code>URI</code> for this object.
 953:    */
 954:   public URI toURI()
 955:   {
 956:     String abspath = getAbsolutePath();
 957: 
 958:     if (isDirectory())
 959:       abspath = abspath + separatorChar;
 960: 
 961:     if (separatorChar == '\\')
 962:       abspath = separatorChar + abspath;
 963:         
 964:     try
 965:       {
 966:         return new URI("file", null, null, -1,
 967:                        abspath.replace(separatorChar, '/'),
 968:                        null, null);
 969:       }
 970:     catch (URISyntaxException use)
 971:       {
 972:         // Can't happen.
 973:         throw (InternalError) new InternalError("Unconvertible file: "
 974:                         + this).initCause(use);
 975:       }
 976:   }
 977: 
 978:   /**
 979:    * This method returns a <code>URL</code> with the <code>file:</code>
 980:    * protocol that represents this file.  The exact form of this URL is
 981:    * system dependent.
 982:    *
 983:    * @return A <code>URL</code> for this object.
 984:    *
 985:    * @exception MalformedURLException If the URL cannot be created 
 986:    * successfully.
 987:    */
 988:   public URL toURL() throws MalformedURLException
 989:   {
 990:     // On Win32, Sun's JDK returns URLs of the form "file:/c:/foo/bar.txt",
 991:     // while on UNIX, it returns URLs of the form "file:/foo/bar.txt". 
 992:     if (separatorChar == '\\')
 993:       return new URL ("file:/" + getAbsolutePath().replace ('\\', '/')
 994:               + (isDirectory() ? "/" : ""));
 995:     else
 996:       return new URL ("file:" + getAbsolutePath()
 997:               + (isDirectory() ? "/" : ""));
 998:   }
 999: 
1000: 
1001:   /**
1002:    * This method creates a directory for the path represented by this object.
1003:    *
1004:    * @return <code>true</code> if the directory was created, 
1005:    * <code>false</code> otherwise
1006:    *
1007:    * @exception SecurityException If write access is not allowed to this file
1008:    */
1009:   public boolean mkdir()
1010:   {
1011:     checkWrite();
1012:     return VMFile.mkdir(path);
1013:   }
1014: 
1015:   /**
1016:    * This method creates a directory for the path represented by this file.
1017:    * It will also create any intervening parent directories if necessary.
1018:    *
1019:    * @return <code>true</code> if the directory was created, 
1020:    * <code>false</code> otherwise
1021:    *
1022:    * @exception SecurityException If write access is not allowed to this file
1023:    */
1024:   public boolean mkdirs()
1025:   {
1026:     String parent = getParent();
1027:     if (parent == null)
1028:       {
1029:         return mkdir();
1030:       }
1031:       
1032:     File f = new File(parent);
1033:     if (!f.exists())
1034:       {
1035:         boolean rc = f.mkdirs();
1036:         if (rc == false)
1037:           return false;
1038:       }
1039: 
1040:     return mkdir();
1041:   }
1042: 
1043:   /**
1044:    * This method creates a temporary file in the specified directory.  If 
1045:    * the directory name is null, then this method uses the system temporary 
1046:    * directory. The files created are guaranteed not to currently exist and 
1047:    * the same file name will never be used twice in the same virtual 
1048:    * machine instance.  
1049:    * The system temporary directory is determined by examinging the 
1050:    * <code>java.io.tmpdir</code> system property.
1051:    * <p>
1052:    * The <code>prefix</code> parameter is a sequence of at least three
1053:    * characters that are used as the start of the generated filename.  The
1054:    * <code>suffix</code> parameter is a sequence of characters that is used
1055:    * to terminate the file name.  This parameter may be <code>null</code>
1056:    * and if it is, the suffix defaults to ".tmp".
1057:    * <p>
1058:    * If a <code>SecurityManager</code> exists, then its <code>checkWrite</code>
1059:    * method is used to verify that this operation is permitted.
1060:    *
1061:    * @param prefix The character prefix to use in generating the path name.
1062:    * @param suffix The character suffix to use in generating the path name.
1063:    * @param directory The directory to create the file in, or 
1064:    * <code>null</code> for the default temporary directory
1065:    *
1066:    * @exception IllegalArgumentException If the patterns is not valid
1067:    * @exception SecurityException If there is no permission to perform 
1068:    * this operation
1069:    * @exception IOException If an error occurs
1070:    *
1071:    * @since 1.2
1072:    */
1073:   public static synchronized File createTempFile(String prefix, String suffix,
1074:                     File directory)
1075:     throws IOException
1076:   {
1077:     // Grab the system temp directory if necessary
1078:     if (directory == null)
1079:       {
1080:         String dirname = System.getProperty("java.io.tmpdir");
1081:         if (dirname == null)
1082:           throw new IOException("Cannot determine system temporary directory"); 
1083:     
1084:         directory = new File(dirname);
1085:         if (! VMFile.exists(directory.path))
1086:           throw new IOException("System temporary directory "
1087:                                 + directory.getName() + " does not exist.");
1088:         if (! VMFile.isDirectory(directory.path))
1089:           throw new IOException("System temporary directory "
1090:                                 + directory.getName()
1091:                                 + " is not really a directory.");
1092:       }
1093: 
1094:     // Check if prefix is at least 3 characters long
1095:     if (prefix.length() < 3)
1096:       throw new IllegalArgumentException("Prefix too short: " + prefix);
1097: 
1098:     // Set default value of suffix
1099:     if (suffix == null)
1100:       suffix = ".tmp";
1101: 
1102:     // Now identify a file name and make sure it doesn't exist.
1103:     File file;
1104:     if (!VMFile.IS_DOS_8_3)
1105:       { 
1106:         do
1107:           {
1108:             long now = System.currentTimeMillis();
1109:             if (now > last_tmp)
1110:               {
1111:                 // The last temporary file was created more than 1 ms ago.
1112:                 last_tmp = now;
1113:                 n_created = 0;
1114:               }
1115:             else
1116:               n_created++;
1117:             
1118:             String name = Long.toHexString(now);
1119:             if (n_created > 0)
1120:               name += '_'+Integer.toHexString(n_created);
1121:             String filename = prefix + name + suffix;
1122:             file = new File(directory, filename);
1123:           }
1124:         while (VMFile.exists(file.path));
1125:       }
1126:     else
1127:       {
1128:         // make sure prefix is not longer than 7 characters
1129:         if (prefix.length() >= 8)
1130:           throw new IllegalArgumentException("Prefix too long: " + prefix + "(valid length 3..7)");
1131: 
1132:         long mask = 0x000000ffffFFFFL >> (prefix.length() * 4);
1133:         do
1134:           {
1135:             int n = (int) (System.currentTimeMillis() & mask);
1136:             String filename = prefix + java.lang.Integer.toHexString(n) + suffix;
1137:             file = new File(directory, filename);
1138:           }
1139:         while (VMFile.exists(file.path));
1140:       }
1141: 
1142:     // Verify that we are allowed to create this file
1143:     SecurityManager sm = System.getSecurityManager();
1144:     if (sm != null)
1145:       sm.checkWrite(file.getAbsolutePath());
1146: 
1147:     // Now create the file and return our file object
1148:     // XXX - FIXME race condition.
1149:     VMFile.create(file.getAbsolutePath()); 
1150:     return file;
1151:   }
1152: 
1153:   /**
1154:    * This method sets the file represented by this object to be read only.
1155:    * A read only file or directory cannot be modified.  Please note that 
1156:    * GNU systems allow read only files to be deleted if the directory it
1157:    * is contained in is writable.
1158:    *
1159:    * @return <code>true</code> if the operation succeeded, <code>false</code>
1160:    * otherwise.
1161:    *
1162:    * @exception SecurityException If the <code>SecurityManager</code> does
1163:    * not allow this operation.
1164:    *
1165:    * @since 1.2
1166:    */
1167:   public boolean setReadOnly()
1168:   {
1169:     // Do a security check before trying to do anything else.
1170:     checkWrite();
1171: 
1172:     // Test for existence.
1173:     if (! VMFile.exists(path))
1174:       return false;
1175: 
1176:     return VMFile.setReadOnly(path);
1177:   }
1178: 
1179:   /**
1180:    * This method returns an array of filesystem roots.  Some operating systems
1181:    * have volume oriented filesystem.  This method provides a mechanism for
1182:    * determining which volumes exist.  GNU systems use a single hierarchical
1183:    * filesystem, so will have only one "/" filesystem root.
1184:    *
1185:    * @return An array of <code>File</code> objects for each filesystem root
1186:    * available.
1187:    *
1188:    * @since 1.2
1189:    */
1190:   public static File[] listRoots()
1191:   {
1192:     return VMFile.listRoots();
1193:   }
1194: 
1195:   /**
1196:    * This method creates a temporary file in the system temporary directory. 
1197:    * The files created are guaranteed not to currently exist and the same file
1198:    * name will never be used twice in the same virtual machine instance.  The
1199:    * system temporary directory is determined by examinging the 
1200:    * <code>java.io.tmpdir</code> system property.
1201:    * <p>
1202:    * The <code>prefix</code> parameter is a sequence of at least three
1203:    * characters that are used as the start of the generated filename.  The
1204:    * <code>suffix</code> parameter is a sequence of characters that is used
1205:    * to terminate the file name.  This parameter may be <code>null</code>
1206:    * and if it is, the suffix defaults to ".tmp".
1207:    * <p>
1208:    * If a <code>SecurityManager</code> exists, then its <code>checkWrite</code>
1209:    * method is used to verify that this operation is permitted.
1210:    * <p>
1211:    * This method is identical to calling 
1212:    * <code>createTempFile(prefix, suffix, null)</code>.
1213:    *
1214:    * @param prefix The character prefix to use in generating the path name.
1215:    * @param suffix The character suffix to use in generating the path name.
1216:    *
1217:    * @exception IllegalArgumentException If the prefix or suffix are not valid.
1218:    * @exception SecurityException If there is no permission to perform 
1219:    * this operation
1220:    * @exception IOException If an error occurs
1221:    */
1222:   public static File createTempFile(String prefix, String suffix)
1223:     throws IOException
1224:   {
1225:     return createTempFile(prefix, suffix, null);
1226:   }
1227: 
1228:   /**
1229:    * This method compares the specified <code>File</code> to this one
1230:    * to test for equality.  It does this by comparing the canonical path names
1231:    * of the files. 
1232:    * <p>
1233:    * The canonical paths of the files are determined by calling the
1234:    * <code>getCanonicalPath</code> method on each object.
1235:    * <p>
1236:    * This method returns a 0 if the specified <code>Object</code> is equal
1237:    * to this one, a negative value if it is less than this one 
1238:    * a positive value if it is greater than this one.
1239:    *
1240:    * @return An integer as described above
1241:    *
1242:    * @since 1.2
1243:    */
1244:   public int compareTo(File other)
1245:   {
1246:     if (VMFile.IS_CASE_SENSITIVE)
1247:       return path.compareTo (other.path);
1248:     else
1249:       return path.compareToIgnoreCase (other.path);
1250:   }
1251: 
1252:   /**
1253:    * This method compares the specified <code>Object</code> to this one
1254:    * to test for equality.  It does this by comparing the canonical path names
1255:    * of the files.  This method is identical to <code>compareTo(File)</code>
1256:    * except that if the <code>Object</code> passed to it is not a 
1257:    * <code>File</code>, it throws a <code>ClassCastException</code>
1258:    * <p>
1259:    * The canonical paths of the files are determined by calling the
1260:    * <code>getCanonicalPath</code> method on each object.
1261:    * <p>
1262:    * This method returns a 0 if the specified <code>Object</code> is equal
1263:    * to this one, a negative value if it is less than this one 
1264:    * a positive value if it is greater than this one.
1265:    *
1266:    * @return An integer as described above
1267:    *
1268:    * @exception ClassCastException If the passed <code>Object</code> is 
1269:    * not a <code>File</code>
1270:    *
1271:    * @since 1.2
1272:    */
1273:   public int compareTo(Object obj)
1274:   {
1275:     return compareTo((File) obj);
1276:   }
1277: 
1278:   /**
1279:    * This method renames the file represented by this object to the path
1280:    * of the file represented by the argument <code>File</code>.
1281:    *
1282:    * @param dest The <code>File</code> object representing the target name
1283:    *
1284:    * @return <code>true</code> if the rename succeeds, <code>false</code> 
1285:    * otherwise.
1286:    *
1287:    * @exception SecurityException If write access is not allowed to the 
1288:    * file by the <code>SecurityMananger</code>.
1289:    */
1290:   public synchronized boolean renameTo(File dest)
1291:   {
1292:     checkWrite();
1293:     dest.checkWrite();
1294:     // Call our native rename method
1295:     return VMFile.renameTo(path, dest.path);
1296:   }
1297: 
1298:   /**
1299:    * This method sets the modification time on the file to the specified
1300:    * value.  This is specified as the number of seconds since midnight
1301:    * on January 1, 1970 GMT.
1302:    *
1303:    * @param time The desired modification time.
1304:    *
1305:    * @return <code>true</code> if the operation succeeded, <code>false</code>
1306:    * otherwise.
1307:    *
1308:    * @exception IllegalArgumentException If the specified time is negative.
1309:    * @exception SecurityException If the <code>SecurityManager</code> will
1310:    * not allow this operation.
1311:    *
1312:    * @since 1.2
1313:    */
1314:   public boolean setLastModified(long time) 
1315:   {
1316:     if (time < 0)
1317:       throw new IllegalArgumentException("Negative modification time: " + time);
1318: 
1319:     checkWrite();
1320:     return VMFile.setLastModified(path, time);
1321:   }
1322: 
1323:   private void checkWrite()
1324:   {
1325:     // Check the SecurityManager
1326:     SecurityManager s = System.getSecurityManager();
1327:     
1328:     if (s != null)
1329:       s.checkWrite(path);
1330:   }
1331: 
1332:   private void checkRead()
1333:   {
1334:     // Check the SecurityManager
1335:     SecurityManager s = System.getSecurityManager();
1336:     
1337:     if (s != null)
1338:       s.checkRead(path);
1339:   }
1340: 
1341:   /** 
1342:    * Calling this method requests that the file represented by this object
1343:    * be deleted when the virtual machine exits.  Note that this request cannot
1344:    * be cancelled.  Also, it will only be carried out if the virtual machine
1345:    * exits normally.
1346:    *
1347:    * @exception SecurityException If deleting of the file is not allowed
1348:    *
1349:    * @since 1.2 
1350:    */
1351:   public void deleteOnExit()
1352:   {
1353:     // Check the SecurityManager
1354:     SecurityManager sm = System.getSecurityManager();
1355:     if (sm != null)
1356:       sm.checkDelete(path);
1357: 
1358:     DeleteFileHelper.add(this);
1359:   }
1360: 
1361:   private void writeObject(ObjectOutputStream oos) throws IOException
1362:   {
1363:     oos.defaultWriteObject();
1364:     oos.writeChar(separatorChar);
1365:   }
1366: 
1367:   private void readObject(ObjectInputStream ois)
1368:     throws ClassNotFoundException, IOException
1369:   {
1370:     ois.defaultReadObject();
1371: 
1372:     // If the file was from an OS with a different dir separator,
1373:     // fixup the path to use the separator on this OS.
1374:     char oldSeparatorChar = ois.readChar();
1375:     
1376:     if (oldSeparatorChar != separatorChar)
1377:       path = path.replace(oldSeparatorChar, separatorChar);
1378:   }
1379:   
1380: } // class File