46 lines
1.4 KiB
Kotlin
46 lines
1.4 KiB
Kotlin
import java.awt.*
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import java.util.concurrent.*
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import javax.swing.*
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class Pendulum(private val length: Int) : JPanel(), Runnable {
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init {
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val f = JFrame("Pendulum")
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f.add(this)
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f.defaultCloseOperation = JFrame.EXIT_ON_CLOSE
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f.pack()
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f.isVisible = true
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isDoubleBuffered = true
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}
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override fun paint(g: Graphics) {
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with(g) {
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color = Color.WHITE
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fillRect(0, 0, width, height)
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color = Color.BLACK
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val anchor = Element(width / 2, height / 4)
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val ball = Element((anchor.x + Math.sin(angle) * length).toInt(), (anchor.y + Math.cos(angle) * length).toInt())
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drawLine(anchor.x, anchor.y, ball.x, ball.y)
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fillOval(anchor.x - 3, anchor.y - 4, 7, 7)
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fillOval(ball.x - 7, ball.y - 7, 14, 14)
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}
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}
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override fun run() {
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angleVelocity += -9.81 / length * Math.sin(angle) * dt
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angle += angleVelocity * dt
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repaint()
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}
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override fun getPreferredSize() = Dimension(2 * length + 50, length / 2 * 3)
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private data class Element(val x: Int, val y: Int)
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private val dt = 0.1
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private var angle = Math.PI / 2
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private var angleVelocity = 0.0
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}
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fun main(a: Array<String>) {
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val executor = Executors.newSingleThreadScheduledExecutor()
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executor.scheduleAtFixedRate(Pendulum(200), 0, 15, TimeUnit.MILLISECONDS)
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}
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