example8_2.java.bak

不错的教程 适合中高级人员的使用

import java.awt.event.*; import java.awt.*;
class 圆 extends Dialog implements ActionListener  //建立对话框类。
{  double r,area;
   TextField 半径=null,
             结果=null;
   Button b=null;
   圆(Frame f,String s,boolean mode)  //构造方法。
   {  super(f,s,mode);
      setLayout(new FlowLayout());
      半径=new TextField(10);
	  结果=new TextField(10);
	  b=new Button("确定");
	  add(new Label("输入半径"));
	  add(半径);add(b);
	  add(new Label("面积是"));
	  add(结果);
	  validate();
	  b.addActionListener(this);       
      setBounds(60,60,260,100);
      addWindowListener(new WindowAdapter()
                      {   public void windowClosing(WindowEvent e)
                           { setVisible(false);
                           }
                      }
                   );
   }
   public void actionPerformed(ActionEvent e)
   { 
	   try{
		   r=Double.parseDouble(半径.getText());
		   area=Math.PI*r*r;
		   结果.setText(""+area);//注意空字符串！
	   }
	   catch(Exception ee)
	   {半径.setText("请输入数字字符");}
   }
}
   
class 三角形 extends Dialog implements ActionListener 
{ double a=0,b=0,c=0,area;
  TextField 边_a=new TextField(6);
  TextField 边_b=new TextField(6);
  TextField 边_c=new TextField(6);
  TextField 结果=new TextField(8);
  Button button=new Button("确定");
   三角形(Frame f,String s,boolean mode)
   {  super(f,s,mode);
      setLayout(new FlowLayout());
      add(new Label("输入三边的长度"));
	  add(边_a);add(边_b);add(边_c);     
      add(button); 
	  add(new Label("面积是："));
	  add(结果);
      validate();
	  button.addActionListener(this);
	  setBounds(60,60,360,100);
	  addWindowListener(new WindowAdapter()
                      {   public void windowClosing(WindowEvent e)
                           { setVisible(false);
                           }
                      }
                   );				   
   }
   public void actionPerformed(ActionEvent e)
   {   try{
		   a=Double.parseDouble(边_a.getText());
		   b=Double.parseDouble(边_b.getText());
		   c=Double.parseDouble(边_c.getText());
		   if(a+b>c&&a+c>b&&b+c>a)
	       { double p=(a+b+c)/2;
		   area=Math.sqrt(p*(p-a)*(p-b)*(p-c));
		   结果.setText(""+area);		   
		   }
           }
	   catch(Exception ee)
	   {结果.setText("请输入数字字符");}
   }
}
class Win extends Frame implements ActionListener
{
	MenuBar bar=null;
	Menu menu=null;
	MenuItem item1,item2;
	圆 circle;三角形 trangle;
	Win()
	{
		bar=new MenuBar();
		menu=new Menu("选择");
		item1=new MenuItem("圆面积计算");
		item2=new MenuItem("三角形面积计算");
		menu.add(item1);menu.add(item2);
		bar.add(menu);
		setMenuBar(bar);
		circle=new 圆(this,"计算圆面积",false);
		trangle=new 三角形(this,"计算三角形",false);
		item1.addActionListener(this);
		item2.addActionListener(this);
		setVisible(true);
		setBounds(100,120,200,190);
		addWindowListener(new WindowAdapter()
                      {   public void windowClosing(WindowEvent e)
                           {setVisible(false);
                           }
                      }
                   );		
	}
		
public void actionPerformed(ActionEvent e)
   {   if(e.getSource()==item1)
	   {circle.setVisible(true);}
       else if(e.getSource()==item2)
	   {trangle.setVisible(true);}
   }

}

public class Example8_2
{  public static void main(String args[])
   {  new Win();
   }
}