lab16_2.java

一个小程序

import java.awt.*;
import java.awt.event.*;
import java.text.NumberFormat;
class TriangleDialog extends Dialog implements ActionListener
{
	TextField edge_a, edge_b, edge_c, answer;
	double a = 0, b = 0, c = 0, area;
	Button but;
	Panel p, p1;
	TriangleDialog(Frame f, String s, boolean b)
	{
		super(f, s, b);
		p = new Panel();
		p1 = new Panel();
		edge_a = new TextField(6);
		edge_b = new TextField(6);
		edge_c = new TextField(6);
		answer = new TextField(6);
		setLayout(new FlowLayout());
		but = new Button("确定");
		add(new Label("输入三角形三条边的长度"));
		p.add(new Label("边_a = "));
		p.add(edge_a);
		p.add(new Label("边_b = "));
		p.add(edge_b);
		p.add(new Label("边_c = "));
		p.add(edge_c);
		add(p);
		p1.add(new Label("面积 = "));
		p1.add(answer);
		p1.add(but);
		add(p1);
		edge_a.addActionListener(this);
		edge_b.addActionListener(this);
		edge_c.addActionListener(this);
		but.addActionListener(this);
		setBounds(100, 100, 450, 200);
		addWindowListener(new WindowAdapter()
		{
			public void windowClosing(WindowEvent e)
			{
				setVisible(false);
			}
		});
	}
	public void actionPerformed(ActionEvent e)
	{
		if(e.getSource() == but || e.getSource() == edge_a || e.getSource() == edge_b || e.getSource() == edge_c)
		{
			try
			{
				a = Double.parseDouble(edge_a.getText());
				b = Double.parseDouble(edge_b.getText());
				c = Double.parseDouble(edge_c.getText());
				if(a + b > c && Math.abs(a - b) < c)
				{
					double p = (a + b + c) / 2;
					area = Math.sqrt(p * (p - a) * (p - b) * (p - c));
					NumberFormat f = NumberFormat.getInstance();
					f.setMaximumFractionDigits(5);
					String s = f.format(area);
					answer.setText(s);
				}
				else answer.setText("不能构成三角形");
			}
			catch(NumberFormatException event)
			{
				answer.setText("含有错误字符");
			}
		}
	}

}
class CircleDialog extends Dialog implements ActionListener
{
	TextField r, answer;
	Button but;
	double l, area;
	Panel p1, p2;
	CircleDialog(Frame f, String s, boolean b)
	{
		super(f, s, b);
		p1 = new Panel();
		p2 = new Panel();
		r = new TextField(6);
		answer = new TextField(6);
		but = new Button("确定");
		p1.add(new Label("输入半径"));
		p1.add(new Label("r = "));
		setLayout(new FlowLayout());
		p1.add(r);
		p2.add(new Label("面积 = "));
		p2.add(answer);
		p2.add(but);
		add(p1);
		add(p2);
		r.addActionListener(this);
		but.addActionListener(this);
		setBounds(120, 120, 300, 200);
		addWindowListener(new WindowAdapter()
		{
			public void windowClosing(WindowEvent e)
			{
				setVisible(false);
			}
		});
	}
	public void actionPerformed(ActionEvent e)
	{
		if(e.getSource() == but || e.getSource() == r)
		{
			try
			{
				l = Double.parseDouble(r.getText());
				area = Math.PI * l * l;
				NumberFormat f = NumberFormat.getInstance();
				f.setMaximumFractionDigits(5);
				String s = f.format(area);
				answer.setText(s);
			}
			catch(NumberFormatException event)
			{
				answer.setText("含有错误字符");
			}
		}
	}
}
class MyFrame extends Frame implements ActionListener
{
	MenuBar bar;
	Menu menu;
	MenuItem triangle, circle;
	TriangleDialog tdialog;
	CircleDialog cdialog;
	MyFrame(String s)
	{
		super(s);
		bar = new MenuBar();
		menu = new Menu("选择");
		triangle = new MenuItem("三角形");
		circle = new MenuItem("圆形");
		tdialog = new TriangleDialog(this, "三角形面积计算", false);
		cdialog = new CircleDialog(this, "圆形面积计算", false);
		bar.add(menu); menu.add(triangle); menu.add(circle);
		setLayout(new GridLayout(1,1));
		add(new Label("选择图形", Label.CENTER));
		setMenuBar(bar);
		setVisible(true);
		setBounds(80, 80, 300, 100);
		validate();
		triangle.addActionListener(this);
		circle.addActionListener(this);
		addWindowListener(new WindowAdapter()
		{
			public void windowClosing(WindowEvent e)
			{
				System.exit(0);
			}
		});
	}
	public void actionPerformed(ActionEvent e)
	{
		if(e.getSource() == triangle)
		{
			tdialog.setVisible(true);
		}
		if(e.getSource() == circle)
		{
			cdialog.setVisible(true);
		}
	}
}
public class Lab16_2 
{
	public static void main(String[] args) 
	{
		MyFrame f = new MyFrame("面积计算");
	}
}