September 2017 Update

Task/Animation/Kotlin/animation.kotlin

@@ -0,0 +1,55 @@
+// version 1.1.0
+
+import java.awt.Dimension
+import java.awt.event.MouseAdapter
+import java.awt.event.MouseEvent
+import java.util.*
+import javax.swing.JFrame
+import javax.swing.JLabel
+
+class Rotate : JFrame() {
+    val text = "Hello World! "
+    val label = JLabel(text)
+    var rotRight = true
+    var startIdx = 0
+
+    init {
+        preferredSize = Dimension(96, 64)
+        label.addMouseListener(object: MouseAdapter() {
+            override fun mouseClicked(evt: MouseEvent) {
+                rotRight = !rotRight
+            }
+        })
+        add(label)
+        pack()
+        defaultCloseOperation = JFrame.EXIT_ON_CLOSE
+        isVisible = true
+    }
+}
+
+fun getRotatedText(text: String, startIdx: Int): String {
+    val ret = StringBuilder()
+    var i = startIdx
+    do {
+        ret.append(text[i++])
+        i %= text.length
+    }
+    while (i != startIdx)
+    return ret.toString()
+}
+
+fun main(args: Array<String>) {
+    val rot = Rotate()
+    val task = object : TimerTask() {
+        override fun run() {
+            if (rot.rotRight) {
+                if (--rot.startIdx < 0) rot.startIdx += rot.text.length
+            }
+            else {
+                if (++rot.startIdx >= rot.text.length) rot.startIdx -= rot.text.length
+            }
+            rot.label.text = getRotatedText(rot.text, rot.startIdx)
+        }
+    }
+    Timer(false).schedule(task, 0, 500)
+}