Applications and Applets An applet is a program delivered via the - - PowerPoint PPT Presentation

applications and applets
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Applications and Applets An applet is a program delivered via the - - PowerPoint PPT Presentation

Applications and Applets An applet is a program delivered via the web security issues, sandbox model where does code/images/etc come from? How is it delivered? what browsers support the 1.1 AWT event model (what about 1.2)? Use


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SLIDE 1

Duke CPS 108

  • 19. 1

Applications and Applets

  • An applet is a program delivered via the web

➤ security issues, sandbox model ➤ where does code/images/etc come from? How is it

delivered?

➤ what browsers support the 1.1 AWT event model (what

about 1.2)?

  • Use IE 4, Netscape 4 (patched), appletviewer to run an applet,

appletviewer is good for debugging

  • Possible to wrap up lots of classes in a .jar file

➤ java archive, similar to a tar file, possible to include .class

files, .au, .gif, etc, so all code transferred at once

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SLIDE 2

Duke CPS 108

  • 19. 2

Running an Applet

  • An applet has an init() method

➤ similar to constructor, called only once, when the applet is

first loaded

  • An applet has a start() method

➤ called each time the applet becomes “active”, run the first

time, or revisited e.g., via the back button in a browser

  • An applet has a stop() method

➤ called when applet is invisible, e.g., user scrolls or goes to

another web page

  • other methods in an applet

➤ destroy, getAppletInfo, getParameterInfo

  • Applet subclasses Panel, so it is an Container/Component
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SLIDE 3

Duke CPS 108

  • 19. 3

Thread

  • Threads are “lightweight” processes

➤ have access to same memory as other threads in the main

process

➤ each thread runs as a separate control, on a multiprocessor

these could be running simultaneously

➤ threads should each get a “time-slice” to run fairly

  • Threads are created by subclassing Thread or implementing

Runnable

➤ Threads have a run method, this is where the action is, but

run is not called directly, only via Thread.start()

  • Must be careful when many threads access the same object,

synchronization is needed