广东自考JAVA语言程序设计一课后习题答案和源代码第七章.docx

1、广东自考JAVA语言程序设计一课后习题答案和源代码第七章第七章 17.1 编写一个应用程序，绘制一个五角星。 17.2 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。 37.3 利用Graphics2D的平移，缩放，旋转功能。绘制一个六角星。 77.4 编写画图程序。 107.5 输入二次曲线的系数，画出二次曲线 177.6. 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.javaimport java.awt.*;import javax.swing.*;/* * 7.1 画一

2、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: F

3、iveStarCanvas.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;

4、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 *

5、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

6、, 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,

7、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.javaimport 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 se

8、rialVersionUID = 1L; private ParabolaCanvas canvas;/ 画出抛物线的花瓣 private JTextField inputA_text, inputB_text, inputC_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

9、); a = 1; b = 0; c = 0; panel = new JPanel(); canvas = new ParabolaCanvas(a, b, c); inputA_text = new JTextField( + a, 3); inputB_text = new JTextField( + b, 3); inputC_text = new JTextField( + c, 3); confirm_button = new JButton(确定); display_label = new JLabel(); panel.add(new JLabel(a = ); panel.a

10、dd(inputA_text); panel.add(new JLabel(b = ); panel.add(inputB_text); panel.add(new JLabel(c = ); panel.add(inputC_text); panel.add(confirm_button); panel.add(display_label); confirm_button.addActionListener(this); inputA_text.addActionListener(this); inputB_text.addActionListener(this); inputC_text.

11、addActionListener(this); setLabel(); this.add(panel, BorderLayout.NORTH); this.add(canvas, BorderLayout.CENTER); this.setBounds(50, 50, 800, 600); this.setVisible(true); this.validate(); this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); public void actionPerformed(ActionEvent e) try a = Double.pa

12、rseDouble(inputA_text.getText(); b = Double.parseDouble(inputB_text.getText(); c = Double.parseDouble(inputC_text.getText(); catch( NumberFormatException Ee ) a = 0; b = 0; c = 0; canvas.set(a, b, c); canvas.repaint(); setLabel(); public void setLabel() String str = 方程：y = ; str += a = 0 ? : (a = 1

13、? x2 : a + x2 ); str += b = 0 ? : (a = 0 ? (b = 1 ? x : b + x ) : (b = 1 ? + x : + + b + x ); str += c = 0 ? : (a = 0 & b = 0 ? c : + + c); display_label.setText(str); public static void main(String args) new ParabolaFrame(); 画抛物线的画板类：ParabolaCanvas.java/* * 画板类，在上面画抛物线 * author 黎明你好 */class Parabol

14、aCanvas extends Canvas private static final long serialVersionUID = 1L; double a, b, c; /* 构造方法，抛物线初始状态 */ public ParabolaCanvas(double a, double b, double c) this.a = a; this.b = b; this.c = c; setBackground(new Color(100, 240, 240); /* * 设置抛物线系数 * param a - 二次项系数 * param b - 一次项系数 * param c - 常数项

15、*/ public void set(double a, double b, double c) this.a = a; this.b = b; this.c = c; public void paint(Graphics g) Graphics2D g2D = (Graphics2D) g; / 画坐标系 g2D.drawLine(0, 300, 600, 300);/ 横线 g2D.drawLine(300, 0, 300, 600);/ 竖线 中心坐标300，300 g2D.drawLine(300, 0, 294, 10); g2D.drawLine(300, 0, 306, 10);

16、/ y轴箭头 g2D.drawLine(600, 300, 590, 294); g2D.drawLine(600, 300, 590, 306);/ x轴箭头 g2D.drawLine(200, 300, 200, 308); g2D.drawString(- 5, 197, 320); g2D.drawLine(100, 300, 100, 308); g2D.drawString(- 10, 97, 320); g2D.drawLine(400, 300, 400, 308); g2D.drawString(5, 397, 320); g2D.drawLine(500, 300, 500

17、, 308); g2D.drawString(10, 497, 320); g2D.drawLine(300, 100, 307, 100); g2D.drawString(10, 310, 103); g2D.drawLine(300, 200, 307, 200); g2D.drawString(5, 310, 203); g2D.drawLine(300, 400, 307, 400); g2D.drawString(- 5, 310, 403); g2D.drawLine(300, 500, 307, 500); g2D.drawString(- 10, 310, 503); g2D.

18、drawString(0,0, 305, 318); g2D.drawString(y轴, 310, 15); g2D.drawString(x轴, 580, 290); for (int i = 0; i 600; i += 20) g2D.drawLine(i, 300, i, 303); g2D.drawLine(300, i, 303, i); / 下面程序为画抛物线 double x0, y0, x1, y1, x2, y2, scale; x0 = 300; y0 = 0; scale = 20.0; g2D.setColor(Color.RED); for (x1 = -15;

19、x1 15; x1 += 0.001D) y1 = a * x1 * x1 + b * x1 + c; x2 = x0 + x1 * scale; y2 = y0 + y1 * scale; g2D.fillOval(int) x2, 300 - (int) y2, 2, 2); 7.3 利用Graphics2D的平移，缩放，旋转功能。绘制一个六角星。程序运行结果：源文件：Work7_3.javaimport java.awt.*;import java.awt.geom.*;import javax.swing.*;/* * 7.3 利用Graphics2D的平移，缩放，旋转功能。绘制一个六

20、角星。 * author 黎明你好 */public class Work7_3 extends JFrame private static final long serialVersionUID = 1L; public Work7_3() super(第七章，第三题); this.add(new SixStarCanvas(80), BorderLayout.CENTER); this.setBounds(50, 50, 400, 400); this.setVisible(true); this.validate(); this.setDefaultCloseOperation(JFra

21、me.EXIT_ON_CLOSE); public static void main(String args) new Work7_3(); 画六角形的画板类：SixStarCanvas.java/* * 画板类，在上面画出六角星 * 通过先画一个三角形，然后旋转6次，得到六角形 * author 黎明你好 */class SixStarCanvas extends Canvas private static final long serialVersionUID = 1L; /* 六角星外接圆的半径 */ private int radius; /* 一个三角形三个顶点的x点坐标集 */ p

22、rivate int xPoints; /* 一个三角形三个顶点的y点坐标集 */ private int yPoints; /* * 构造方法 * param r - 初始化外接圆半径 */ public SixStarCanvas(int r) this.radius = r; xPoints = new int r, 2 * r, (int) (3 * r / 2) ; yPoints = new int r, r, (int) (r - Math.sqrt(3) * r / 2) ; public void paint(Graphics g) Graphics2D g2D = (Gra

23、phics2D) g; BasicStroke bs = new BasicStroke(1, BasicStroke.CAP_SQUARE, BasicStroke.JOIN_MITER); g2D.setStroke(bs); AffineTransform trans = new AffineTransform(); trans.translate(10, 10);/ 移动 trans.scale(2, 2);/ 放大 for (int i = 1; i = 6; i+) trans.rotate(60.0 * Math.PI / 180, radius, radius);/ 旋转 g2

24、D.setTransform(trans); g2D.drawPolygon(xPoints, yPoints, 3); 7.4 编写画图程序。程序运行结果：控制画板的窗口类源文件：PaintFrame.javaimport java.awt.*;import java.awt.event.*;import javax.swing.*;/* * 7.4 编写画图程序。 * 控制画板的窗口类 * author 黎明你好 */public class PaintFrame extends JFrame implements ItemListener, ActionListener private

25、static final long serialVersionUID = 1L; /* 画板 */ private PaintCanvas canvas; /* 画笔端点装饰，无装饰、圆形装饰、方形装饰 */ private JToggleButton cap_butt, cap_round, cap_square; /* 橡皮 */ private JToggleButton eraser; /* 画笔大小 */ private JComboBox width_box; /* 选择颜色的按钮 */ private JButton selectColor; /* 单选按钮分组 */ priva

26、te ButtonGroup group; private JPanel panel; private String item; private int strokeWidth = 1, strokeCap = 0, strokeJoin = BasicStroke.JOIN_BEVEL; public PaintFrame() super(画图小程序); canvas = new PaintCanvas(); selectColor = new JButton( ); cap_butt = new JToggleButton(标准); cap_round = new JToggleButto

27、n(圆形); cap_square = new JToggleButton(方形); eraser = new JToggleButton(橡皮); panel = new JPanel(); group = new ButtonGroup(); item = new String20; for (int i = 0; i 20; i+) itemi = + (i + 1); width_box = new JComboBox(item); width_box.setEditable(true);/ 组合框可以输入 cap_butt.setSelected(true);/ 笔形，标准为开始默认

28、 canvas.setPenColor(Color.BLACK); selectColor.setBackground(Color.BLACK);/ 画笔颜色，开始为黑色 / 添加监控 width_box.addItemListener(this); width_box.addActionListener(this); selectColor.addActionListener(this); cap_butt.addItemListener(this); cap_round.addItemListener(this); cap_square.addItemListener(this); eraser.addItemListener(this); / 画笔形式单选按钮 group.add(cap_butt); group.add(cap_round); group.add(cap_square); group.add(eraser); / 添加按钮 panel.setLayout(new FlowLayout(); panel.setBorder(BorderFactory.createTitledBorder(设置区); panel.add(new JLabel(笔形：); panel.add(ca