Libraries

Library functions are imported

External Java classes, fields and methods are imported into the HolonJ program. Define a local word, which represents the class, field or method. You can then address the item locally.

importClass: List   java.awt.List    

imports class java.awt.List, which is now accessible as the local word List.

importMethod: AddList      List add ( string -- )

imports the method add from the class java.awt.List. The class is indicated here by its local name List, therefore the class must be imported first. 

static importField: InStream    System in InputStream

The word InStream represents the variable in of type InputStream in the class java.lang.System. 

Collection of imports

This macro view presents the collection of Java imports that have accumulated to date. You probably find the Java functions that you need here. Otherwise just add them to the library.

 

Typical uses

• Frame
• Graphics
• Threads
• Textoutput
• Strings
• Streams
• Files
• Date
• Events

Frame

The frame is a window that can be moved and resized, but has no actions yet. For example the close button is not active. 

This class defines a close action, which simply ends the program.

class: wAction extends WindowAdapter

i: wa.<init>   ( -- )   initsuper ()  ;

i: wa.windowClosing   ( windowevent e -- )
      0 getRuntime runExit  ; 

Here is a frame for a game of TicTacToe.

class: TicTacToe extends Frame

i: ttt.<init>   ( -- )
      " TicTacToe" initsuper ( string -- )
      300 300 this setSize
      this showWindow
      new wAction ()  this addWindowListener  ;

Graphics

The display part of the frame is its Graphics context. 

Graphics myGraphics

: PaintImage   (  -- ) 
     " image.gif" getImageFile
      10 10  this  this getGraphics drawImage  ;

x1 y1 x2 y2 myGraphics drawLine

Color myColor
green red blue new myColor ( int int int -- )

Font myFont
" font" style size new myFont ( string int int -- )

 font = TimesRoman etc,  style = bold, italic, plain

myFont myGraphics setFont
myColor myGraphics setColor

Threads

1. Clock as a subclass of Thread.

class: Clock extends Thread

\ The thread action, overwrites run
i: Clock.run   ( -- )
    begin this repaint 1000. sleep again  ;

: Clock.main   ( string [] args -- )
    clock myClock  new myClock ()
    myClock startThread  ;

2. Clock applet implementing Runnable.

class: Clock extends Applet implements Runnable

Thread myThread

\ The thread action, overwrites run
i: Clock.run   ( -- )
    begin this repaint 1000. sleep again  ;

\ starting the thread
i: Clock.start   ( -- )
    myThread null? if  this new myThread ( runnable -- )  then
    myThread startThread  ;

Output to console

." This text is printed"  \ prints the text
" Text string" type       \ prints a string
55 .                            \ prints a number
7 ##.                          \ prints a leading zero if the number is only one digit

Strings

" string1" " string2"   "+      
          " test string"   "=  if ... 

Stringbuf Text                 \ a text buffer
0 Text setLength             \ empty the buffer
( char -- ) Text caddBuf    \ add char to the buffer
Text stringOf                   \ convert the buffer contents to a string 

Streams

InputStreams deliver bytes, Readers provide characters. HolonJ gets bytes and reads characters.

importMethod: getByte      InputStream read ( -- int )

Files

importClass: File    java.io.File
importMethod: exists   File exists ( -- boolean )

: filetest  ( string name -- )
    file theFile   name new theFile ( string -- ) 
    theFile exists  if   ." File exists"  else ." doesn't exist"  then  ;

Stringbuf Text      
FileInputstream Input

i: getText   ( file myFile -- )
    myFile new Input ( file -- )  0 Text setLength
    begin Input getByte dup -1 <> while Text caddBuf drop repeat  ;

Date

\ prints current date and time
: printDate  ( -- ) 
      new Date ()  toString type  ;

Events

importMethod: addButtonListener  
      Button addActionListener ( ActionListener -- )

i: addButton ( string btext -- )
      btext new Button ( string -- )
      dup Controlpanel addComp
      this swap addButtonListener ;

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