:



 ,
 




1. 

2. , WWW  

3. Java, Joe, NEO

4. Java -   
4.1.  Java
4.1.1.    Java
4.1.2.   
4.1.3. 
4.1.4.  
4.1.5.  
4.1.6.  
4.2.  Java
4.2.1.    Java-
4.2.2. Java-
4.2.3. Java  
4.2.4. Java WorkShop
4.3.  Java  :  
4.3.1.  
4.3.2.      (  )
4.3.3.   
4.3.4. 
4.3.5.   Component,    

5. Joe -   Java-    -
-

6. 




      Java,    
"   ". ,  ,    -
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 (. 1).

.  1.     Java ( 
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. 3.     

        
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.

-, Web-    -
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 15 .    .

Java-      .
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Web-,       ,  
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,     Java.



    Java -  -  ,
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,       ,  Web-
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     .

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,      ,   
Web-     , -
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,    (,  ),
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.           
      WWW,   
,         
,    .  ,  
   ,    Java, 
  (. 6).

. 6.    Java-   -
.

   ?

     -       
  Java    .  
  Sun Microsystems    -
  -  NEO  (NEtworked Objects,  ). 
NEO   CORBA  (Common  Object  Request
Broker  Architecture),    . 
     
NEO       -
       ,  
 ,         -
     (. 7).

.  7.    
.

 ,         
   Java-  NEO-. , 
      -
  ( Java   , -
  C/C++,      ),    
     , Java   
 ""  MS-Windows.    1996  -
 SunSoft           
Joe,          
 Java-       ,
       
NEO (. 8).

. 8.    Java, Joe  NEO.

 ,       
    -.      
    Java.      
 ,   Joe.






   Java  ,  , -
    ,    C++.



    -  -
,    :

- 

- 

- .

     Java    
 .



    Java  C++  .  
   ;      -
.      ,    
 (        -
      Java-).

1     class Point extends Object {
2       private double x;
3       private double y;

4       Point (double x, double y) {
5         this.x = x;
6         this.y = y;
7       }

8       Point () {
9         this (0.0, 0.0);
10      }

11      public void setX (double x) {
12        this.x = x;
13      }

14      public void setY (double y) {
15        this.y = y;
16      }
        . . .
17    }

    Java      () 
 .   class  
       .  , -
      .

            
extends ( 1).  Object -    -
.    Java    -"":   , 
Object,  .    -
    .

     (private, protected,  public)
  ,       C++,    .  
 ,  ,      
    (. ).

  9       
.

         
 - .    Java      .
  ,     ( -
      ).   
,   ,    
finalize.         -
 ,  .

  this (., ,  5  9)  
     .      -
    super:

1     class ThreePoint extends Point {
2       protected double z;

3       ThreePoint () {
4         super ();
5         z = 0.0;
6       }

7       ThreePoint (double x, double y, double z) {
8         super (x, y);
9         this.z = z;
10      }
11    }

  4  8    .

  ,    Java,      C++,
    ,      -
       .

  C++,       static    
    ,         
. ( ,  ,   -
 ,   Java  .)   
   java.lang.

1 public final
2 class Character extends Object {

3     public static final int MAX_RADIX = 36;

4     static char downCase[];

5     static {
6         char down[] = new char[256];
7         for (int i = 0 ; i < 256 ; i++) {
8             down[i] = (char) i;
9       }
10        for (int lower = 'a' ; lower <= 'z' ; lower++) {
11            int upper = (lower + ('A' - 'a'));
12            down[upper] = (char)lower;
13      }

14        for (int lower = 0xE0; lower <= 0xFE; lower++) {
15            if (lower != 0xF7) { // multiply and divide
16                int upper = (lower + ('A' - 'a'));
17                down[upper] = (char)lower;
18            }
19        }
20      downCase = down;
21    }

22    public static boolean isLowerCase(char ch) {
23      return (upCase[ch] != ch);
24    }

25 }

       Java  C++.

  5  21      
  ,      
 Java-.        
Character.

  1  3    final.      1
                 
Character.   3       const  
C++.

  final    ,   -
      -.

      C++,   Java    , 
    .  ,   -
  ,   .  -
 (   )        abstract.
          
.

  Java    ,  -
   java.lang.  . 9   
.

. 9.     Java.

       Class. -
      Class (,  
      ).     Class
     getClass,   -
  Object.

  Class      -
   ""   .    
 Class,  ,   :

1    public native String getName();
2    public native Class getSuperclass();
3    public static native Class forName(String className)
         throws ClassNotFoundException;

 forName        .
  native    ,   
,     Java- (, -
   C).



    Java     -
  C++.  -,   Java   .
-,        -
    (    final   
). -,   Java     -
  C++  .

     . :

public interface Verbose {
  public void drawOn (Graphics g);
  public void printOn (OutputStream os);
}

public class Star extends Polygon implements Verbose {
  public void drawOn (Graphics g) {
  //   
  }
  public void printOn (OutputStream os) {
  //   
  }
}

public class Text extends StringBuffer implements Verbose {
  public void drawOn (Graphics g) {
  //   
  }
  public void printOn (OutputStream os) {
  //   
  }
}

public class Blackboard extends Canvas {
  public void drawVerbose (Verbose d) {
    Graphics g = getGraphics ();
    d.drawOn (g);
  }
}

 Verbose   .    
      ,  -   
 .

   Star            
(Polygon).    ,        
   (Blackboard)      .

   Text       
       .

 Blackboard -   Canvas,  -
    .     ,    
     ,  -
   (  Object).

 ,        -
   .   
     ,   -
 .



     new.  -
        . 
   -  new  . .

Point myPoint = new Point ();

    (    new)  
Java  .

    ,      ( 
            -
).           .
 ,    ,   -
    .

     ,    
        
 (   ). .

  Point p = new Point (100.0, 100.0);
  . . .
  p = new Point (1.0, 1.0);
  //     (100, 100)   

  {
     String s = new String ("Local string");
     System.out.println (s);
  }
  //   "Local string"   

        
finalize. - ,       -
,  finalize  .



  Java     ,  
  .    .

      Java  ,  , 
   .

-  :
- - byte - 8 ,
- - short - 16 ,
- - int -  32 ,
- - long - 64 .
   ,  unsigned   .

-    :
- - float - 32 ,
- - double - 64 .
    IEEE 754.

- char
  char  16-     (
0-65535).     Unicode.  -
         
  Java-.

- boolean
   true  false,     -
   .

  Java, ,  .   -
. 

Point myPoints[];

  myPoints       Point.
       


myPoints = new Point[10];

          
  null.

         -
:

howMany = myPoints.length;

   (  )   Java
,    ,   ..   Java  -
.

,           String
( )    StringBuffer  (  ).
,

String hello = "Hello world!";



   Java   .  , 
   ,       -
,         ,  
       private
 protected.

    .  "  "
   Java  .

      

package my_packages.pack1:

  package           
Java-.     .

      -
 import. ,

import java.util;
import java.util.HashTable;
import java.util.*;

  import      
util  :

util.Vector
util.HashTable
. . .

      HashTable,  
         ,  
 util.

   import     -
     util.



   Java  ,   -
         ( , 
 ). .

test:
  for (int i = 0; i < 10; i++) {
    for (int j = 0; j < 10; j++) {
      if (i > 3) {
        break test;
      }
    }
  }

        break,
  continue (    ).

 goto   Java .



   ,    -
  ,   Java   try/
catch/finally.  try  ,    
     .  
     catch   
 . ,  finally    -
,          
    try.       try-
        (break, return 
..)  finally   .

      
  -   Throwable. , 
ArrayIndexOutOfBoundsException      -
   ,  OutOfMemoryException -  -
     ,  ClassCastException
-                     ,     
InterruptedException  -     
 ..        String,
              .   
getMessage   .

       -
.  ,    InterruptedIOException 
,     ,   -
  .

      
messages.          -
,          
. (,           
).

try {
  for (int i = 0; i < 100; i++) {
    System.out.println (messages[i]);
  }
}

catch (ArrayOutOfBoundException e) {
  System.out.println ("No more messages");
}
catch (Exception e) {
  System.out.println ("Unexpected exception");
  System.out.println (e.getMessage());
}

finally {
  System.out.println ("Work done");
}

      -
  

throw new MyException ("Something's wrong");

  Java    
 .    ( Error)  -
,       ( 
 Java-).    ( Exception) -
  ,     -
.       -
   ,       
  try/catch/finally,      
  

throws Exception1, Exception2, ...

.

class Foo extends Object {
  . . .
  public void readFromFile (String fn) throws InvalidFormatException {
    FileInputStream fis;
    try {
      fis = new FileInputStream (fn);
      //    .
      . . .
      //     ,
      //   :
      throw new InvalidFormatException ("Wrong format");
      . . .
    }
    catch (FileNotFoundException e) {
      //   
    }
    finaly {
      if (fis != null )
        fis.close(); //   ,    
    }
  }
  . . .
}

     readFromFile    -
  .     ,    -
.                 
readFromFile.       ,
    .      
  .



   -    
.      -
 ,    ,  -
        .  
   ,    Java    
       .

  Java     Thread, -
  Runnable,   synchronized  
 Object wait  notify.

4.1.6.1.  Thread   Runnable

 (thread)       
 .  ,     ,
 ,    .

            start()  
Thread.  ,    -
,    run(). ,     run()  -
     ; 
     ,    .

            
run(),              Thread
stop()    destroy().     
.

         -
   suspend(), sleep()  yeild().

 ,     suspend, -
    resume().

  sleep()      
 .

    yeild()    
 ;       -
.

Java-  .   -
,  Java-   . 
,        -
    . ,   -
   .  ,     
     ,  , -
       -  -
 suspend(), sleep()  yeild().

 . 10    .

. 10.   .

       -
    "/".  -
  ,   Mark Tillotson    -
  comp.lang.java.

class my_producer extends Thread
{
  int items_to_do ;
  my_buffer the_buffer ;

  my_producer (my_buffer buf, int count)
    { super() ;
      the_buffer = buf ;
      items_to_do = count ;
    }

  public void run ()
    {
      while (items_to_do > 0)
        { System.out.println ("producer to_do = " + items_to_do) ;
          Integer item = new Integer (items_to_do*items_to_do) ;
          the_buffer.insert (item) ;
          items_to_do-- ;
        }
      System.out.println ("producer exiting") ;
    }
}

       .

       my_producer  -
  Thread,      -
 ,   run().   ,
 ,     -  -
    ,    
    Runnable.    -
    - run(). .

1  class SomethingToRun extends BaseRunner implements Runnable {
2    private Thread aThread;
3    public void run () {
       //  
    . . .
4    }

5    SomethingToRun () {
6       aThread = new Thread (this);
7       aTread.start ();
8    }
9  }

  6   .   -
   SomethingToRun, , , 
         run()
 .   start()   7      
   .



           , 
Java         
.        "-
/".

      ,   ,
   Java,    , -
  70-  -.

 Java-    , 
   synchronized.   -
  ,  synchronized  
 () .    
(  )     

synchronized () ;

       .

      -
       .
     .

 wait()      , 
        -
     ,   - -
      notify()  notifyAll(). -
        
     .

class my_buffer
{
  Object [] vec = new Object [8] ;
  int ip = 0 ;
  int ep = 0 ;

  synchronized void insert (Object item)
    {
      do
        {
          if (ip-ep < 8)
            { vec [(ip++) & 7] = item ;
              if (ip-ep == 1) notify () ;  // ,    
              return ;
            }
          try wait () ;  catch (InterruptedException e) ;
        } while (true) ;
    }

  synchronized Object extract ()
    {
      do
        {
          if (ip > ep)
            { Object result = vec [(ep++) & 7] ;
              if (ip-ep == 7) notify();  // ,    
              return result ;
            }
          try wait () ; catch (InterruptedException e) ;
        } while (true) ;
    }
}

class my_producer extends Thread
{
  int items_to_do ;
  my_buffer the_buffer ;

  my_producer (my_buffer buf, int count)
    { super() ;
      the_buffer = buf ;
      items_to_do = count ;
    }

  public void run ()
    {
      while (items_to_do > 0)
        { System.out.println ("producer to_do = " + items_to_do) ;
          Integer item = new Integer (items_to_do*items_to_do) ;
          the_buffer.insert (item) ;
          items_to_do-- ;
        }
      System.out.println ("  ") ;
    }
}

class my_consumer extends Thread
{
  int items_to_do ;
  my_buffer the_buffer ;

  my_consumer (my_buffer buf, int count)
    { super() ;
      the_buffer = buf ;
      items_to_do = count ;
    }

  public void run ()
    {
      while (items_to_do > 0)
        { System.out.println ("consumer to_do = " + items_to_do) ;
          Object item = the_buffer.extract () ;
          System.out.println ("consumer got " + item) ;
          items_to_do-- ;
        }
      System.out.println ("  ") ;
      synchronized (this){
        notify () ; //     
                    // (. con.wait()  main())
      }
    }
}

public class threaded3
{
  public static void main (String [] args) throws InterruptedException
    {
      my_buffer the_buffer = new my_buffer () ;
      my_producer prod = new my_producer (the_buffer, 40) ;
      my_consumer con  = new my_consumer (the_buffer, 40) ;

      Thread.currentThread().setPriority (5) ;
      prod.setPriority (4) ;  //     
      con.setPriority  (3) ;  //    

      prod.start() ;
      con.start() ;
      synchronized (con)
        {
          con.wait() ;  //      
                        //  
        }
      System.out.println ("    ") ;
    }
}

     ,  .
        .     insert() 
extract()  my_buffer  wait()    -
 .   ,   notify()   -
    .  ""    
   ,   . ,   ""
 insert(),      -
,          
.    ,  insert()  .





 ,   , , -
    ,  ,   
Java-  ,       
,      -  -
      -
   (. xxx).

. xxx.   Java-

  ,  ,   Java-  
     -      
,        ,   
WWW-.

   ,        
      .

      

public static void main (String args[]);

       public-,   
,   Java-.
  args    -   .

: ,   

public class myTop {
  public static void main (String args[]){
    int argc = args.length;

    for (int i = 0; i < argc; i++)
      System.out.println (argc[i]);
  }
}

          
    Applet:

public void init ()     ;
public void start ();     ;
public void stop ();  ,      Web-;
public void destroy ();     
          ;  ,    ; 
           stop();        
           .

   :

1     import java.awt.Graphics;
2     import java.applet.Applet;

3     class SimpleApplet extends Applet {
4       public void paint (Graphics g) {
5         g.drawString ("Hello world!", 10, 10);
6       }
7     }

 public void paint (Graphics g) (  4-6)  ,
        ,   -
  WWW-   .

   WWW-   .
  HTML 2.0    
 .          -
     ,  . 
      WWW-   -
,     .

       WWW-.





    ,      Java 



 WWW-   ,  
,   Java,   

--------------------------------------------------------------------------
    ,      Java
--------------------------------------------------------------------------

 ,     , 
 :

public void init () {
  String fontname = getParameter ("name");
  String fontSizestring = getParameter ("size");
  int theSize = Int.parseInt (fontSizeString);
  . . .
}


    4.2.2. Java-


Java-         Java-
   Java-.  , Java- -
    ,         -
    ,    -
  ,   -  -
 . ,         
        
  Java-.

  , ,  .  -
       P-     -
  -;      
    ;     -
-,       .

    Java    -
   ,    Java-
        --
  .   ,    
,         Java-.
  Web-  Java-,    -
  . ,  ,  Java- 
   ;       
    . , -
       Java-  
,     .  
 ,   Java-   (-
           ), 
  ()    .      
,      Java-, 
 -.

   Java-  .  
     1.0.


    4.2.2.1.  ,  Java-


Java-     :

- byte -       ;

- short -   ;

- int -   ;

- long -   ;

- float -      IEEE-754;

- double -   ;

- char -      Unicode.

  Java-      
 ,      -
       .  
    ,     
 . ,        
    iadd,     
  -  dadd.

  boolean    -
     .

     :

- object -     (  
 );

- returnAddress -     .

  Java-     -
.   Sun Microsystems   object -
  ,    -    
  .    .

Java-    32-.       
(long,  double)     .
 ,       ;
  ,  -    
,  ""   .


    4.2.2.2. 


 Java-    :

- pc  -   ;      ,
   .

- vars -        -
 .

- optop -     . Java- -
 ,        
      .

- frame -   ,    
.

    ,     
  :  ,   -
    .

   ,   -
         -
 .       -
       (   
   ).     -
         
  .

          
    .

       Java-  
           
 catch,   .

        -
  , , ,  ,  
 Java-       
.


    4.2.2.3.  


          
 .  Java   ,   
  ,        
  .     , -
  Java-.


    4.2.2.4.   Java-


 Java-      ,  
   (  ).  
  :

-         . 
        .  ,
     dload  ,  ,
           
  ,     aload      
.

-        .

-   . ,    newarray  
,   ,    
 ,         .
,       - -
  , anewarray.      
   Java-.

-       .     ,
 , ,        
  ,    ,   -
  .

-  .     ;  
  .

-   (, , ,  ).

-     .

-   . ,   jsr (
 )     ;
  ,     jsr,    
.     .

-    .     
      .  -
,    breakpoint,   -
         -
.

-       (/-
 / ).

-   .  .  invokevirtual  -
 ()      
.   invokenonvirtual    -
    - ,   -
 .  invokestatic    
  . ,  invokeinterface  ,
 .      -
       ,    
  .

-     - athrow.

-    ( ,    -
).

-    (   ,  
).

 ,       
Java  Java-.   ,    -
  Java-     
 .


    4.2.3. Java  


       
   ,   .   -
           
 Java-,    Web-  -
   .   ,  
  Java        
  .

      , 
  goto    "".  
          
,      ..      -
        ,
,      
,       .

, ,      ""  -
        
 .   -   -
,   ,  ,      
  Java-.

  , ,   ,   
     ,   
    ,  ,   
 .  ,      -
        (   UNIX,
     fork  exec),   
     ,   -
  Java-.

    ,       
 Java-          
  .  ,  Netscape Navigator 2.0  
     .  
 ,   JDK 1.0    Sun  Microsystems
   ,     -
.

 ,       :

-   ;

- // ;

-  ;

-     - ,   ,
.

  JDK     ,    -
   ~/.hotjava/properties  

acl.read=/home/welcome
acl.write=/tmp

       -
-.    ,     -
 ,        
,        , 
    ,    -
  ,      .. 
       
.     finally  -
  .

  ,      
      
  .   ,  ,  Argus  System
Group,        
 ,          
       "-
"  .   ,   
  ,    -
  Java-.  ,  -
        
     ,   Java.


    4.2.4. Java WorkShop


      1996   Sun Microsystems  
  1.0   Java WorkShop.   
   :     -
 Java   ,   Web-.  .  y1
      Java WorkShop.

. y1.       Java WorkShop.

  ,    , -
,     .  -
,    ,  ,      
        .  , 
     .

Java WorkShop     ,  
  , , ,   -
 .    :

-   -    ,  -
  ,       
.

-  -      
.      -
  ,         
  ..

-  -         
.      , -
 Web-       -
,         , 
   .

-    -      
Java-.

-    -    
   .

-     .     
 Java WorkShop,      -
 .

- .     ,    Java
WorkShop      
,     Java-.    
y2       .

.  y2.              Java
WorkShop.

-  .

Java WorkShop       SPARC/Solaris  
Intel/Solaris,    Microsoft Windows 95/NT. - -
     Java WorkShop  . -
 45   , 32 ( Solaris)    16
( Windows)   .

,       -
             
   .


     * 4.3.  Java  :  



    4.3.1.  


    Java   ,    
,    -  -
.  ,    Java  -
    .    
 .

    (    -
) ,      -
  (  )  .    -  -
    .  -
      ,    
    .

  ,     -   ,  -
  ,      -
.  Motif        MS-Windows      
Macintosh.  -     -
, -   , -
     ..

  ,       -    
    .  -
,   -  -
,  ,   ,  ,  , ,
   ,      -
.  ,  ,    "  -
", " "  ..

    ,    --
     - -
    ,     -
 .

     ,  ,  -
      -
, ""   .    
   MFC, OWL, Zink   .

        Java-  AWT 
Abstract Windowing Toolkit -     -
.

AWT        
 .  ""   ,   ,
    ,    -
.  AWT          ,  
, ,  ;     -
    - , ,  . 
   . x1.

. x1.     AWT.

       ,  
 Peer.

      AWT,   
 .   -     -
         
 Java.


    4.3.2.          ( 

)

     ,    ,
          ,  
.  AWT     (    
       Component),   -
      .  -
,     -   ,  
      .  ,  -
 .     . x2.  (
         Charles L. Perkins,
clp@home.HarvardSq.com.)

. x2.   AWT

 . x3  ,   . x2.

    :

- Button
- Checkbox
- Label
- List
- ScrollBar
- TextArea
- TextField

 :

- Dialog
- FileDialog
- Frame
- Panel
- Window

      -
    ,     -
.


    4.3.3.   


  ,     , 
  . ,     ,  -
         .
    (,     ,   )
        -
.    ,  ,  -
      (,  -
, " ").    -
   ,       -
       ,   -
   .

AWT        .  
        
   ,        
         .
         
    Layout  (). Layout  ,
       ,  
   .

  AWT  5  :

- BorderLayout
- CardLayout
- FlowLayout
- GridLayout
- GridBagLayout

       . x4.

. x4.     AWT.

      Object  
  LayoutManager.

  LayoutManager        Container.  
  Container   3  add,  
    .      -
     add,   
    LayoutManager        .      
LayoutManager   setLayout.

 ,      -
.


    4.3.3.1. BorderLayout


BorderLayout      5  
: , , ,   :

[Image]

        -


add (string, component);

.

setLayout (new BorderLayout());
buttonN = new Button ("one");
add ("North", buttonN);
// ...   


    4.3.3.2. CardLayout


[Image]

    .    -
   .  ,  CardLayout  -
          . C
   .

    :

add (string, component);

 string -  "",  component -    -
.    ,        
(        -
):

setLayout (new CardLayout ());
add ("one", create (new FlowLayout ()));
add ("two", create (new BorderLayout ()));
add ("three", create (new GridLayout (2, 2)));
add ("four", create (new BorderLayout (10, 10)));
add ("five", create (new FlowLayout (FlowLayout.LEFT, 10, 10)));
add ("six", create (new GridLayout (2, 2, 10, 10)));


    4.3.3.3. FlowLayout


FlowLayout      .
     .  -
      
 .

[Image]

setLayout (new FlowLayout ());
add (new Button ("OK"));
add (new Button ("Cancel"));
add (new Button ("Resume"));

       

add (component).

     , ,   -
.


    4.3.3.4. GridLayout


   .     
  .    ,  
 .    .

       

add (component)

[Image]

.

setLayout (new GridLayout (2, 3)); // 2 , 3 
add (new Button ("1"));
add (new Button ("2"));
add (new Button ("3"));
add (new Button ("I"));
add (new Button ("II"));


    4.3.3.5. GridBagLayout


GridBagLayout      -
 .      
     .    ,  GridBagLayout
      .  
    GridBagConstraints.

      10 , -
    .  ,  
GridBagConstraints,    :

GridBagLayout gridbag = new GridBagLayout ();
GridBagConstraints c = new GridBagConstraints ();
setLayout (gridbag);

//  
c.fill = GridBagConstraints.BOTH;
c.weightx = 1.0;
. . .
Button button1 = new Button ("1");
gridbag.setConstraints (button1, c);
add (button1);
. . .
//     
//   GridBagConstraints,
// 
// c.fill =  GridBagConstraints.NONE;
Button buttonX= new Button ("X");
gridbag.setConstraints (buttonX, c);
add (buttonX);


    4.3.4. 


  AWT,       ,   
   .   - -
  ,         AWT    
ACTION_EVENT.

 ,     AWT 
  ,  .  , -
          
.

  ,     AWT.  
       (,  
   ) .   ,  
-   (, ),  -
  handleEvent.       ,
    ,    ,  -
    (,   ).
  ,     ,  -
  (  )  .

        
       .

- -,        
       ,    
   .

- -,       -
,       handleEvent.

    .    -
    ,     
 .

              -
handleEvent    , -
        -
      (,   -
).

 ,      , -
        . 
         
    "The Command Class for AWT objects", -
  Jan Newmarch, jan@ise.canberra.edu.au.


    4.3.5.   Component,    


    Component,    -
 .

- postEvent().  ,  ,  -
    .

-         handleEvent(). 
  ,      ,  
    ,  

- - action()
- - keyUp()
- - mouseDown()
- - gotFocus()

 ..

  handleEvent()     .   ,
 ,       -
    , ,  handleEvent() -
  false,    handleEvent()  , -
  .

  AWT      Event, 
   :

public Object target; //  
public long when;     // ,   
public int  id;       //  (KEY_PRESS, MOUSE_DOWN...)
public int  x;        // 
public int  y;        // 
public int  key;      //  
public int  modifiers;//   (control, shift ...)
public Object arg;    //  
public Event evt;     //      

    ,    -
    (       -
).

class MyApplet extends Applet {
. . .
  public boolean action( Event evt, Object arg) {
    . . .
    if ((ev.target instanceof Button) && arg.equals ("OK")) {
      //   
      . . .
      return true;
    } else {
      //  
      . . .
    }
    . . .
    return false;
  }
  . . .
}

   ,      Button  -
 "OK",      -
  true,      .

       -
 . .

class OKButton extends Button {
  . . .
  public boolean action (Event e, Object arg) {
    //   
    . . .
    return true;
  }
}

 ,       Java    
 .     -
   .



    5.  Joe -   Java-

  -

,   "Java, Joe  NEO",    ,    
    SunSoft  -  Joe -   
  ,      Java,  
    ,     NEO. 
 Joe     (  )   -
,       , -
       Java-  -
    .

   Jet Info    "-
 ".        .  
         Java   -
   ,   .

1  import java.awt.Font;
2  import java.awt.Color;

3  public class JAVAhello extends java.applet.Applet {
4    Font f = new Font ("TimesRoman", Font.BOLD, 36);

5    public void init () {
6      resize (150, 25);
7    }

8    public void paint (Graphics g) {
9      g.setFont (f);
10     g.setColor (Color.blue);
11     g.drawString ("Hello, World!", 50, 25);
12   }
13 }

    Joe,   -
    /.

1  import sunw.services.*;
2  import java.awt.Graphics;
3  import java.awt.Font;
4  import java.awt.Color;

5  public class JOEhello extends sunw.services.JOEApplet {
6    sunw.corba.ObjectRef obj;
7    Hello.HelloWorldRef hiThere;

8    Font f = new Font("TimesRoman", Font.BOLD, 36);

9    public void init () {
10     super.init ();
11     resize (150, 25);

12     obj = find ("HelloWorldServer");
13     hiThere = Hello.HelloWorldStub.narrow (obj);
14   }

15   public void paint (Graphics g) {
16     g.setFont (f);
17     g.setColor (Color.red);
       //     ,   C++,
       //   .
18     g.drawString (hiThere.sayHello (), 50, 25);
19   }
20 }

   ,     -
.

  1        
.

    5  ,      Hello  
JOEApplet.

  6   ( )  
 NEO-.      
   .

  7     NEO-, 
       (
,   )   Java.

  12      NEO    
 .

  13      
 .

,   18     -
, ,  ,    Java (,  
C++).  ,        -
,     .

     Joe  .  -
   :

-    NEO-,      
IDL (Interface Definition Language),     Java. 
       Joe  IDL - Java.
     ,    
      
  ,     . 
 ,  ,    Joe,  -
        WWW-
  Java-.

-        Java    
     Joe   
 .

 Java-     -
.

,        -
,       .
 ,       
 -.      
Joe   Java-  IDL-.



    6. 


   Java -    ,  -
    .  -
      -
,          
      .  , -
       -
 -     .

Java   Web-,    -
  -. Java   - -
  -     . -
,        -
     .

       Sun Microsystems - Joe  NEO - Java
     
,        -
    .

------------------

      ,   
   .    ,
  1993 ,   Sun Microsystems.   
          Java,  
     Java,   -
 Java-   Java.

 1996            
         
  Java.

        Java,
        -
        1996   
"Hooked on Java".


. Internet, Web  Java    
    .       
        -  
     Java,     
        -
,    ,     -
,   ,    
    Java   -
.

         -
     ,    -
  Internet,  , Java-  ..
         -
 .

     ,       
     ,     -
?

.  ,  Java    Internet  
        ,
        ,
          
 .   ,    
    ,      
   .      , 
Java  Internet        ,
  .      
    ,     
  .

    Java  Internet?  ,     -
         
,    :     -
   .

.   , Java      -
.  ,    ,   
  Java (,   - )?  
      Java?

.     ,    
      ,    Java, 
    .  ,    -
   ,      . -
    ,    ,  -
  .

   ,      ,   
Java,          ,  
  Java,   ?

.           ,
  Internet,  Web   Java,   
   (IBM, Sun, HP, DEC, Compaq, Oracle   -
)?

.        -
          
   .     -
.        -
  Java,  ,      
,     ,  Microsoft, 
          . 
          -
     ,  ,  
,    ,     -
  .

.  ,     , -   , -
     . 
,          
" "   80- .   -
      ,   
  -    . -
    ,     Java  
  " ",     
      .  ,   ,
       Java  -
   " "?

.        Java- .
 Internet     -
     ,        
.       ,    
,          
   .

.       Java?

.     ,  
,     
,  ,  3D-.  Java,
  -     3D-
,      . -
           
  .     Java,    3D--
        -
.

.   Internet, Web  Java  ,  -
 ,   .    -      
    Java      
    .    -
,          -
,             
?

.  ,   ,    
      Java.     
Internet -   .   
         .
      Sun   ,    
       Java.

. Netscape  Microsoft      Web-
.  Netscape    70%  ,  Microsoft -
        -
  .    ,       
    .     Sun  -
  HotJava  -    Web-.  ,
 - ,   Netscape,  Microsoft   -
    ,   Sun ?

.     HotJava,  , 
  HotJava              
Internet.  Netscape Navigator,  Internet Explorer  
  ,          
 .   HotJava Sun  -
  ,   ,      
Java.         ,
   Java,      
    .

.          -
   Internet, Web  Java?

.  Internet -       -
.          ,    
Internet        ,
    ,    . 
         !

.    ?

.    OLE!


Last-modified: Tue, 21 May 1996 18:44:14 GMT

  :