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自考JAVA语言程序设计(一)课后习题答案和源代码(第七章)

第七章1 7.1 编写一个应用程序，绘制一个五角星。1 7.2 用Graphics2D绘制一条抛物线，设抛物线方程的系数从图形界面输入。3 7.3 利用Graphics2D的平移，缩放，旋转功能。绘制一个六角星。7 7.4 编写画图程序。10 7.5 输入二次曲线的系数，画出二次曲线17 7.6. 写音乐播放器，只能播放wav，mid格式的。24 第七章 7.1 编写一个应用程序，绘制一个五角星。 程序运行结果： 源文件：Work7_1.java import java.awt.*; import javax.swing.*; /** * 7.1 画一个五角星 * @author 黎明你好 */ public class Work7_1 { public static void main(String args[]) { JFrame win = new JFrame(“第七章，第一题“); win.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); win.setBounds(50, 50, 210, 250); win.add(new FiveStarCanvas(100), BorderLayout.CENTER); win.setVisible(true); win.validate(); } } 画板类源文件: FiveStarCanvas.java /** * 画板类，在上面画出五角星 * @author 黎明你好 */ class FiveStarCanvas extends Canvas { private static final long serialVersionUID = 1L; /** 五角星外接圆的半径 */ private int radius; /** * 构造方法 * @param r - 初始化外接圆半径 */ public FiveStarCanvas(int r) { this.radius = r; } public void paint(Graphics g) { int ax = radius; int ay = 0; int bx = (int) (radius * (1 - Math.cos((18 * Math.PI) / 180))); int cx = (int) (radius * (1 + Math.cos((18 * Math.PI) / 180))); int dx = (int) (radius * (1 - Math.cos((54 * Math.PI) / 180))); int ex = (int) (radius * (1 + Math.cos((54 * Math.PI) / 180))); int by = (int) (radius * (1 - Math.sin((18 * Math.PI) / 180))); int cy = (int) (radius * (1 - Math.sin((18 * Math.PI) / 180))); int dy = (int) (radius * (1 + Math.sin((54 * Math.PI) / 180))); int ey = (int) (radius * (1 + Math.sin((54 * Math.PI) / 180))); g.setColor(Color.RED); g.drawLine(dx, dy, ax, ay); g.drawLine(ax, ay, ex, ey); g.drawLine(ex, ey, bx, by); g.drawLine(bx, by, cx, cy); g.drawLine(cx, cy, dx, dy); g.setColor(Color.BLUE); g.drawOval(0, 0, 2 * radius, 2 * radius); g.drawLine(radius, radius, ax, ay); g.drawLine(radius, radius, bx, by); g.drawLine(radius, radius, cx, cy); g.drawLine(radius, radius, dx, dy); g.drawLine(radius, radius, ex, ey); } } 7.2 用Graphics2D绘制一条抛物线，设抛物线方程的系数从图形界面输入。 程序运行结果： frame源文件：ParabolaFrame.java import java.awt.*; import java.awt.event.*; import javax.swing.*; /** * 7.2 用Graphics2D画抛物线，抛物线方程的系数从图形界面输入. * @author 黎明你好 */ public class ParabolaFrame extends JFrame implements ActionListener { private static final long serialVersionUID = 1L; private ParabolaCanvas canvas;// 画出抛物线的花瓣 private JTextField A_text, B_text, C_text; // 三个文本框，接收方程系数 private JButton confirm_button;// 确定按钮 private JLabel display_label; private JPanel panel;// 布局面板 private double a, b, c;// 抛物线三个系数 public ParabolaFrame() { super(“第七章，第二题“); a = 1; b = 0; c = 0; panel = new JPanel(); canvas = new ParabolaCanvas(a, b, c); A_text = new JTextField(““ + a, 3); B_text = new JTextField(““ + b, 3); C_text = new JTextField(““ + c, 3); confirm_button = new JButton(“确定“); display_label = new JLabel(); panel.add(n