Java Q&A

<b>(a)</b>
skij> (define button (new 'java.awt.Button "Press Me"))
  <<< #<java.awt.Button[button0,0,0,0x0,invalid,label=Press Me]>

<b>(b)</b>
skij> (invoke button 'setLabel "Please Press Me")
skij> (define window (new 'java.awt.Frame))
  <<< #<java.awt.Frame[frame1,0,0,0x0,invalid,hidden,layout=java.awt.Border   Layout,resizable,title=]>
skij> (invoke window 'setVisible #t)
skij> (invoke window 'add button)
;;; Hm, we still can't see anything
skij> (invoke window 'getSize)
  <<< #<java.awt.Dimension[width=112,height=27]>
skij> (invoke window 'setSize 300 200)
;;; The window grows, but still we can't see the button!
skij> (invoke window 'show)

<b>(c)</b>
(invoke-static 'java.lang.Thread 'sleep (long 100))

<b>(d)</b>
skij> (peek (invoke button 'getSize) 'width)
  <<< 292

<b>(e)</b>
skij> (peek-static 'java.lang.System 'out)
  <<< #<java.io.PrintStream@3ae82e8c>

<b>(f)</b>
skij> (define listener (new 'com.ibm.jikes.skij.misc.GenericCallback
                            (lambda (event)
                               (print "That tickles!"))))
  <<< #<com.ibm.jikes.skij.misc.GenericCallback@8bbc2e8c>
skij> (invoke button 'addActionListener listener)

Example 1: Scheme primitives and examples. (a) Arguments; (b) invoke; (c) invoke-static; (d) peek; (e) peek-static; (f) applying a procedure to an event. In these interactive examples, "skij>" is the prompt, what follows is typed by users. If a value is returned, it is printed after "<<<." Java objects that are not standard Scheme types are quoted with the "#<...>" notation.