Java IO.pdf - Nguyen Dang Binh

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Java I/O • Do not parse pathnames to find directories. Use the methods of the java.io.File class instead. • Do not use renameTo() for anything except renaming a file. In particular, do not use it to move a file. • Try to avoid moving and copying files from within Java programs if at all possible. • Do not use . to refer to the current directory. Use System.getProperty ("user.dir") instead. • Do not use .. to refer to the parent directory. Use getParent() instead. • Do not assume the current working directory is the one where your .class files live. It almost certainly won't be that directory on the Mac, and it may not be on other platforms, including Windows and Unix. • Place any data files your program requires in JAR archives rather than directly in the filesystem, then load them as resources from the class path. • When in doubt, it never hurts to convert filenames to canonical form. • Do not assume anything about filesystem conventions. Some platform somewhere will surprise you. (Have you tested your program on BeOS yet?) • Test your code on as many different filesystems as you can get your hands on. Despite all the problems I've pointed out, it is mostly possible to write robust file access code that works across all platforms where Java runs. But doing so requires understanding, effort, and thought. You cannot simply write for Windows or Unix and hope things will work out for the best on other platforms. You must plan to handle a wide range of filesystems and filename conventions. 305
Chapter 13. File Dialogs and Choosers Java I/O Filenames are problematic, even if you don't have to worry about cross-platform idiosyncrasies. Users forget filenames, mistype them, can't remember the exact path to files they need, and more. The proper way to ask a user to select a file is to show them a list of the files in the current directory and get them to select from that list. You also need to allow them to navigate between directories, insert and remove floppy disks, mount network servers, and more. Most graphical user interfaces (and not a few nongraphical ones) provide standard widgets for selecting a file. In Java the platform's native file selector widget is exposed through the java.awt.FileDialog class. Like many native peer-based classes, however, FileDialog doesn't behave exactly the same on all platforms. Therefore, Swing (part of the Java Foundation Classes) provides a pure Java implementation of a file dialog, the javax.swing.JFileChooser class. [1] JFileChooser (and Swing in general) has much more reliable cross-platform behavior. 13.1 File Dialogs I'm going to jump out of the java.io package for a minute to pick up one file-related class from the AWT, java.awt.FileDialog. File dialogs are the standard open and save dialogs provided by the host GUI. Users use them to pick a directory and a name under which to save a file or to choose a file to open. The appearance varies from platform to platform, but the intent is the same. Figure 13.1 shows a standard Save dialog on the Mac; Figure 13.2 shows a standard open dialog on Solaris. Figure 13.1. The Mac's standard Save dialog 1 The package name for Swing has changed several times since its first early access release. javax.swing is its final home—this package name is used in Swing 1.1 (for use with JDK 1.1) and Java 2 (which includes Swing and the rest of JFC). For more information about Swing, see Java Swing, by Robert Eckstein, Marc Loy, and Dave Wood (O'Reilly & Associates, 1998). 306
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Java I/O Elliotte Rusty Harold Publ
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III: Filter Streams ...............
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V: Appendixes .....................
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Preface Java I/O In many ways this
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Java I/O operations from moving byt
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Chapter 9 Chapter 10 Java I/O Chapt
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Chapter 17 Java I/O lining up the d
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Security Issues Java I/O I don't kn
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Java I/O Finally, although many of
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Part I: Basic I/O Java I/O 13
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Java I/O The word stream is derived
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Java I/O The java.util.jar package
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Java I/O For instance, according to
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Java I/O Java understands several d
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Java I/O commonly use an eight-bit
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Java I/O For the most part, these c
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Figure 1.1. An xterm console on Uni
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Java I/O If you absolutely must use
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Java I/O in Apple's Macintosh Runti
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Java I/O to work inside a web brows
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Java I/O bit pattern to a particula
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Java I/O The output is the same as
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OutputStream out = new NullOutputSt
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Figure 2.1. The StreamedTextArea co
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Java I/O When you call read(), you
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Java I/O try { byte[] b = new byte[
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Java I/O Once you have closed an in
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public class StreamCopier { } publi
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Chapter 4. File Streams Java I/O Un
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} } for (int i = 0; i < args.length
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Java I/O The FileOutputStream class
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Java I/O ASCII format is the defaul
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} } } Java I/O if (hex >= 16) Syste
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Java I/O Finally, many HTML files c
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Java I/O In particular, URL connect
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Java I/O Example 5.3 uses these ste
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Java I/O many available ports but o
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Java I/O inspecting the port. It kn
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} } } String response = "Hello " +
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} public void actionPerformed(Actio
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Chapter 6. Filter Streams Java I/O
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Java I/O output stream, out. Among
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Java I/O SourceFile???StringExtract
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6.3 Buffered Streams Java I/O Buffe
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public boolean markSupported() Java
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The compiler rewrites this complica
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public class TeeCopier { } public s
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} } try { FileInputStream fin = new
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} public int available() throws IOE
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public class HexFilter extends Dump
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} } StreamCopier.copy(in, out); in.
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Java I/O the java.io.DataOutput int
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Java I/O Although other schemes are
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} public static void main(String ar
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Java I/O Since Java has no unsigned
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dout.close(); } catch (IOException
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Java I/O The DataInputStream class
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Java I/O The readLine() method read
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7.7 Miscellaneous Methods Java I/O
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public synchronized void write(int
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** * Writes a 4 byte Java float to
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} * possible that this number is te
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*/ public byte readByte(int b) thro
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} Java I/O long byte4 = in.read();
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7.9 Thread Safety Java I/O The Litt
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public static void main(String[] ar
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Table 7.2. Command-Line Switches fo
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} protected void fill() throws IOEx
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Chapter 8. Streams in Memory Java I
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UDP Byte array input and output str
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} } try { // So that the buffer doe
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Java I/O Otherwise, these classes j
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} } catch (IOException e) { // prob
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Java I/O legally unencumbered—tha
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Java I/O if it doesn't, it will com
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Java I/O The first method fills the
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public class DirectDeflater { } pub
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9.1.2.1 Constructing inflaters Ther
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9.1.2.7 An example Java I/O Example
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Java I/O stream itself, without hav
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Java I/O Each inflater input stream
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Java I/O This writes all remaining
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} } } FileOutputStream fout = new F
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} } } catch (IOException e) {System
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Java I/O Normally, the name argumen
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% java FancyZipLister temp.zip test
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Java I/O All high-order Unicode byt
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Java I/O the files to be stored in
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9.3.3.2 Open the next zip entry Jav
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Java I/O Better checksum schemes us
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} } int b; while ((b = in.read()) !
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Java I/O example, under Unix, to ma
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Java I/O archive. If the signatures
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Java I/O public JarFile(String file
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Java I/O The java.util.jar.Attribut
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9.5.7 Manifest Java I/O What the ja
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public ZipEntry getNextEntry() thro
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Java I/O so throw a java.lang.Unsup
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within the space of the next few li
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Chapter 10. Cryptographic Streams J
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Java I/O • It should be difficult
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Figure 10.1. The four steps to calc
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Java I/O you only want to detect si
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public void reset() Java I/O In pra
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Java I/O After each successful call
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} byte[] result = md.digest(); for
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} } catch (Exception e) {System.err
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public class EasyFileDigest { publi
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Java I/O them your encryption (publ
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Java I/O DES, triple DES (DESede),
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IDEA RC2 RC4 Blowfish Java I/O The
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Figure 10.2. Encrypting data Java I
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} } catch (NoSuchAlgorithmException
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} } Java I/O } catch (InvalidKeySpe
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SecretKey blowfishKey = blowfishKey
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Java I/O public final byte[] doFina
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Java I/O A CipherInputStream object
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10.6.2 CipherOutputStream CipherOut
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} } byte[] newDigest = sha.digest()
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} } else if (args[firstFile].equals
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Java I/O Note how little we had to
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Chapter 11. Object Serialization Ja
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Java I/O To write an object onto a
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Java I/O Needless to say, this is a
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Java I/O java.awt.image.renderable
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Java I/O are not serializable, then
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11.5.1.5 Making nonserializable fie
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Java I/O output streams, but DataIn
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Figure 11.2. The serialver GUI Java
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public SerializableZipFile(File fil
Page 262 and 263: public class NetworkWindow extends
Page 264 and 265: private void writeObject(ObjectOutp
Page 266 and 267: } } Vector v = (Vector) oin.readObj
Page 268 and 269: Java I/O the resolveClass() method
Page 270 and 271: Example 11.6. Person import java.ut
Page 272 and 273: public class SealedPoint { } public
Page 274 and 275: Chapter 12. Working with Files Java
Page 276 and 277: Java I/O not begin with an @. Under
Page 278 and 279: Java I/O placing a minus sign befor
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Page 282 and 283: System Properties System properties
Page 284 and 285: Java I/O complete list of the ASCII
Page 286 and 287: Win32 index.html MacOS index.html N
Page 288 and 289: Java I/O The path argument should b
Page 290 and 291: Java I/O assume the array returned
Page 292 and 293: Example 12.2. Paths import java.io.
Page 294 and 295: String canonicalPath = f.getCanonic
Page 296 and 297: Java I/O The isHidden() method, onl
Page 298 and 299: 12.3.4 Manipulating Files Java I/O
Page 300 and 301: fin.close(); src.delete(); Java I/O
Page 302 and 303: public int hashCode() public boolea
Page 304 and 305: public class DirList { } File direc
Page 306 and 307: 12.4 Filename Filters Java I/O You
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Page 314 and 315: Figure 13.2. Motif standard Open di
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Page 322 and 323: 13.2.2 Displaying File Choosers Jav
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Page 326 and 327: Figure 13.4. The choosable file fil
Page 328 and 329: Example 13.7. JavaChooser import ja
Page 330 and 331: 13.2.7 Selecting Directories Java I
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Page 334 and 335: 13.2.12.1 Action events Java I/O Wh
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Page 338 and 339: 13.3 File Viewer, Part 6 Java I/O W
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Page 344 and 345: Java I/O Chapter 14. Multilingual C
Page 346 and 347: Java I/O the upper 128 characters o
Page 348 and 349: makeBlock("Telugu", 0x0C00, 0x0C7F)
Page 350 and 351: } } for (int i = 0; i < names.lengt
Page 352 and 353: 14.3 Unicode Escapes Java I/O Curre
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Java I/O The most common type of ch
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Java I/O encoding into a new file c
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Java I/O String openingLineInUnicod
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Java I/O For example, given some Wr
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The flush() and close() methods flu
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15.4 The InputStreamReader Class Th
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Java I/O Similarly, to write text i
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Java I/O These methods behave like
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Java I/O Since string objects are i
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This class has three constructors t
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Do not use the newLine() method if
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Example 15.5. The cat Program impor
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There are four constructors in this
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PipedReader pr = new PipedReader();
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Example 15.7. SourceReader package
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Java I/O question is what to do if
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Java I/O numeric data. If they choo
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} public boolean isText() { if (thi
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default: } } else { LittleEndianInp
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public void init() { } this.addWind
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Chapter 16. Formatted I/O with java
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Java I/O variable salary 12 places
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Hebrew Hebrew Israel iw Hungarian R
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For example: Java I/O NumberFormat
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public void setMaximumIntegerDigits
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Java I/O Like other aspects of text
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Example 16.5. PercentTable import j
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Java I/O align the decimal points i
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Figure 16.1. The PrettiestTable app
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Java I/O This whole class is just a
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Java I/O Most number formats are in
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public int getMultiplier() public v
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Arabic (Saudi Arabia) Arabic (Sudan
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Slovak #,##0.### -1 234,56 #,##0.00
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16.6.2.1 Utility methods Java I/O F
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** * Concrete class for formatting
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} String integerField = digits.subs
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Chapter 17. The Java Communications
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javax.comm.CommPortIdentifier@be4c9
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} } } switch(com.getPortType()) { c
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Java I/O In this example, you see t
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17.2.5 Registering Ports For comple
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} public void run() { } try { byte[
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Java I/O The output buffer size is
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Java I/O Here's the results for bot
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Java I/O If the requested values ar
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Figure 17.1. PC DB-25 serial port t
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public abstract void setRTS(boolean
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Java I/O Steps 1 and 2 should be fa
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Java I/O standard messages on other
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Java I/O serial port events: when t
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17.5.5.3 Step 3 Java I/O In many ci
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Appendix A. Additional Resources Ja
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A.5 Data Compression Java I/O Java
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Java I/O "Developing International
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Appendix B. Character Sets Java I/O
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151 epa (end of guarded area) 183
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Java I/O Cp857 DOS ASCII plus Turki
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Java I/O As extensive as this list
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