回答編集履歴
1
１クラスにまとめた
test
CHANGED
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@@ -81,3 +81,84 @@
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81
81
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通常GUIプログラムではコンソール入出力は使用しません。
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83
83
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UI部品（コンポーネント）を使って、簡単に操作できるようにしましょう。
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84
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85
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---
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86
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87
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追記
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88
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１クラスにまとめました。これなら間違いなく実行できるでしょう^^
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89
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90
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```Java
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91
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import javax.swing.*;
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import java.awt.Color;
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import java.awt.Graphics;
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import java.util.Scanner;
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95
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96
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public class Test1 extends JPanel {
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97
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public static void main(String[] args) {
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Scanner stdIn = new Scanner(System.in);
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int n;
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while (true) {
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System.out.println("正何角形？3-999:");
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try {
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n = stdIn.nextInt();
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if (3 <= n && n <= 999) break;
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} catch (Exception ignored) { stdIn.next(); }
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106
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}
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107
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108
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JFrame gw = new JFrame("円と正多角形");
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gw.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
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gw.setSize(1000, 1000);
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gw.setLocationRelativeTo(null);
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112
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gw.add(new Test1(n));
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gw.setVisible(true);
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}
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private int n;
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public Test1(int n) {
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this.n = n;
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printApproximationPI();
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122
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SpinnerNumberModel model = new SpinnerNumberModel(n, 3, 999, 1);
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JSpinner spinner = new JSpinner(model);
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spinner.addChangeListener(e -> {
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this.n = (int) spinner.getValue();
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repaint();
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printApproximationPI();
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});
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add(spinner);
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}
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@Override public void paintComponent(Graphics g) {
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super.paintComponent(g);
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int x0 = getWidth() / 2;
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int y0 = getHeight() / 2;
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int r = Math.min(x0, y0) / 5 * 4;
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g.setColor(Color.BLUE);
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g.drawOval(x0 - r, y0 - r, r * 2, r * 2);
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int[] x = new int[n];
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int[] y = new int[n];
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double delta = 2 * Math.PI / n;
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for (int i = 0; i < n; i++) {
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x[i] = (int) (Math.cos(-Math.PI / 2 + delta * i) * r) + x0;
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y[i] = (int) (Math.sin(-Math.PI / 2 + delta * i) * r) + y0;
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}
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g.setColor(Color.RED);
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g.drawPolygon(x, y, n);
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}
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private void printApproximationPI() {
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double a = n;
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double b = 180 / a;
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double m = Math.toRadians(b);
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double l = a * (Math.sin(m));
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System.out.println("正" + n + "角形の円周率の近似:" + l);
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}
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}
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```
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