通过实例可以更好的了解java

12-例子1
import java.applet.*;
import java.awt.*;
public class Example12_1 extends Applet
{ Button button1,button2;Label label1,label2;
  TextArea text;
  public void init()
  { setLayout(new BorderLayout());  
    text=new TextArea(" ",10,10);
    button1=new Button("东");  button2=new Button("西");
    label1=new Label("上北");  label2=new Label("下南");    
    add("North",label1);add(label2,"South");
    add(button1,"East");add(button2,"West"); 
    add(text,"Center");
  }   
}



12-例子2
import java.applet.*;import java.awt.*;
import java.awt.event.*;
class Mycanvas extends Canvas
{ int x,y;
  Mycanvas(int a,int b)
  { x=a;y=b;
    getSize();
  }
 public void paint(Graphics g)
  {g.setColor(Color.red);
   g.fillOval(50,50,4*x,4*y);//画实心椭圆
   g.drawString("我是第 "+x,20,90);
  }
 public Dimension getPreferredSize()
  {return new Dimension(200,100);   }
} 
public class Example12_2 extends Applet implements ActionListener
{ CardLayout mycard;
  Button button1,button2,button3;
  Mycanvas mycanvas[];
  Panel p; 
  public void init()
  { setLayout(new BorderLayout());
//小容器的布局是边界布局
    mycard=new CardLayout();
    p=new Panel();
    p.setLayout(mycard);//p的 布局设置为mycard（卡片式布局）
    button1=new Button("first");button2=new Button("next");
    button3=new Button("last one"); mycanvas=new Mycanvas[21]; 
    for(int i=1;i<=20;i++)
      { mycanvas[i]=new Mycanvas(i,i);
        p.add("I am "+ i ,mycanvas[i]);//向p添加画布组件，先加入的是"卡片"式的第一张。
      }
    button1.addActionListener(this);
    button2.addActionListener(this);
    button3.addActionListener(this);
    Panel p2=new Panel();
p2.add(button1);p2.add(button2);
p2.add(button3);
    add(p,"Center");add(p2,"South");
  }
  public void actionPerformed(ActionEvent e)
  { if(e.getSource()==button1)
     { mycard.first(p);
     }
   else if(e.getSource()==button2)
     { mycard.next(p);
     }
   else if(e.getSource()==button3)
     { mycard.last(p);
     }
  }
 }
}



12-例子3
import java.applet.*;
import java.awt.*;
public class Example12_3 extends Applet
{ Button button1,button2,button3,button4,button5,button6;
  Label label1,label2,label3;
  GridLayout net;
  public void init()
  { net=new GridLayout(5,3); 
    setLayout(net);  
    button1=new Button("赵");
    button2=new Button("钱");
    button3=new Button("孙 ");
    button4=new Button("李 ");
    button5=new Button("周 ");
    button6=new Button("吴 ");     
    label1=new Label("郑",Label.CENTER);
    label2=new Label("王",Label.CENTER);
    label3=new Label("姓",Label.CENTER);
    add(button1)  ; add(button2)  ;  add(button3);
    add(new Label()); add(new Label());  add(new Label());
    add(button4)  ; add(button5)  ;  add(button6);
    add(new Label()); add(new Label());  add(new Label());
    add(label1)   ; add(label2)   ;  add(label3)   ; 
  }   
}



12-例子4-1
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
class Mypanel1 extends Panel
  //扩展Panel类
{ Label label ;  
  Mypanel1() 
//构造方法。当创建面板对象时，
//面板被初始化为有一个标签。
  {  setLayout(new GridLayout(1,1));   //布局为GridLayout(1,1)。
     label=new Label("计算从数a到数 b的连续和",Label.CENTER);
     add(label);
  }
}
class Mypanel2 extends Panel //扩展Panel类。
{ Label label1,label2;TextField text1,text2;Button button;   
  Mypanel2()  //构造方法。当创建面板对象时,面板被初始化为有两个标签，
  {          　　 //两个文本框，一个按钮，布局为GridLayout(1,5)。 
     label1=new Label("输入起始数:"); 
     label2=new Label("输入终止数:");
     text1=new TextField(10);   text2=new TextField(10);
     button=new Button("确定");
     setLayout(new GridLayout(1,5));
     add(label1);add(text1);add(label2);add(text2);add(button);
  }
}
class Mypanel3 extends Panel //扩展Panel类
{ Label label;TextField text;   
  Mypanel3()  //构造方法。当创建面板对象时,面板被初始化为有一个标签，
  {  label=new Label("计算的结果:");//一个文本框，布局为GridLayout(1,3)。
     text=new TextField(10);
     setLayout(new GridLayout(1,3));
     add(label);add(text);add(new Label());
  }
}
public class Example12_4 extends Applet implements ActionListener
{ Mypanel1 panel1;Mypanel2 panel2;Mypanel3 panel3;
  GridLayout net;
  public void init()
  { net=new GridLayout(3,1);
    setLayout(net);  
    panel1=new Mypanel1();  
    panel2=new Mypanel2();
    panel3=new Mypanel3();    
    add(panel1);add(panel2);add(panel3);
    (panel2.button).addActionListener(this);
  }   
  public void actionPerformed(ActionEvent e)
  { if(e.getSource()==(panel2.button))
     { long n1,n2,sum=0; 
       n1=Long.parseLong( panel2.text1.getText());  
       n2=Long.parseLong( panel2.text2.getText());
       for(long i=n1;i<=n2;i++)
         { sum=sum+i;
         }
      panel3.text.setText(String.valueOf(sum));  
     }  
  }
}



12-例子4-2
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
public class Example124_1 extends Applet implements ActionListener
{ Label label_1 ,label_2,label_3,label_4;
  TextField text1,text2,text3; Button button;
  GridLayout net;
  public void init()
  { net=new GridLayout(3,1);
    setLayout(net); 
    label_1=new Label("计算从数a到数 b的连续和",Label.CENTER);
    Panel p1=new Panel();p1.setLayout(new GridLayout(1,1));
    p1.add(label_1);
    add(p1);  
    label_2=new Label("输入起始数:");label_3=new Label("输入终止数:"); 
    text1=new TextField(10); text2=new TextField(10);
    button=new Button("确定");
    Panel p2=new Panel();p2.setLayout(new GridLayout(1,3));
    p2.add(label_2);p2.add(text1);p2.add(label_3);
    p2.add(text2);p2.add(button);
    add(p2);
    label_4=new Label("计算的结果:");text3=new TextField(10);
    Panel p3=new Panel();p3.setLayout(new GridLayout(1,3));
    p3.add(label_4);p3.add(text3);p3.add(new Label());
    add(p3); 
    button.addActionListener(this);
  }   
  public void actionPerformed(ActionEvent e)
  { if(e.getSource()==button)
     { long n1,n2,sum=0; 
       n1=Long.parseLong( text1.getText());  
       n2=Long.parseLong( text2.getText());
       for(long i=n1;i<=n2;i++)
         { sum=sum+i;
         }
      text3.setText(String.valueOf(sum));  
     }  
  }
}



12-例子5
import java.applet.*;import java.awt.*;import java.awt.event.*;
class Panela extends Panel
{ Button b1; Button b2; Button b3; Button b4; Button b5; Button b6; 
   Button b7; Button b8; Button b9; Button b10; Button b11; Button b12;
Panela()
 { setLayout(new GridLayout(4,3));
 b1=new Button("sin(a)"); b2=new Button("cos(a)"); b3=new Button("tan(a)");
 b4=new Button("asin(a)"); b5=new Button("acos(a)"); b6=new Button("atan(a)");
 b7=new Button("pow(a,b):a的b次幂"); b8=new Button("abs(a):绝对值");
 b9=new Button("sqrt(a):平方根");   b10=new Button("exp(a)"); 
   b11=new Button("log(a):自然对数");b12=new Button("max(a,b)");
   add(b1) ; add(b2); add(b3);  add(b4) ; add(b5); add(b6);  
   add(b7) ; add(b8); add(b9);  add(b10) ; add(b11); add(b12);  
 }
}
class Panelb extends Panel
{ Label label;
  Panelb()
 { setLayout(new GridLayout(1,1));
   label=new Label("计算器",Label.CENTER);
   add(label);
 }
}
class Panelc extends Panel
{ TextField text1,text2;
 Panelc()
 {setLayout(new GridLayout(1,4));
  text1=new TextField() ;text2=new TextField();
  add(new Label("输入数a")) ; add(text1);add(new Label("输入数b")) ;add(text2);
 }
}
class Paneld extends Panel
{ TextField text;
 Paneld()
 {setLayout(new GridLayout(1,2));
  text=new TextField() ;
  add(new Label("计算结果："));add(text);
 }
}
public class Example12_5 extends Applet implements ActionListener
{ Panela A;Panelb B;Panelc C;Paneld D;
 public void init()
 {setLayout(new GridLayout(4,1));
 A=new Panela();B=new Panelb();C=new Panelc();D=new Paneld();
 add(B);add(C);add(A);add(D);
 A.b1.addActionListener(this);A.b2.addActionListener(this);A.b3.addActionListener(this);
 A.b4.addActionListener(this);A.b5.addActionListener(this);A.b6.addActionListener(this);
 A.b7.addActionListener(this);A.b8.addActionListener(this);A.b9.addActionListener(this);
 A.b10.addActionListener(this);A.b11.addActionListener(this);
A.b12.addActionListener(this);
 }
public void actionPerformed(ActionEvent e)
{ double a,b,c;
 if(e.getSource()==A.b1)
  { a=Double.valueOf(C.text1.getText()).doubleValue();
    c=Math.sin(a);
    D.text.setText(String.valueOf(c));
  }
 else if(e.getSource()==A.b2)
  { a=Double.valueOf(C.text1.getText()).doubleValue();
    c=Math.cos(a);
    D.text.setText(String.valueOf(c));
  }
 else if(e.getSource()==A.b3)
  { a=Double.valueOf(C.text1.getText()).doubleValue();
    c=Math.tan(a);
    D.text.setText(String.valueOf(c));
  }
 else if(e.getSource()==A.b4)
  { a=Double.valueOf(C.text1.getText()).doubleValue();
    c=Math.asin(a);
    D.text.setText(String.valueOf(c));
  }
 else if(e.getSource()==A.b5)
  { a=Double.valueOf(C.text1.getText()).doubleValue();
    c=Math.acos(a);
    D.text.setText(String.valueOf(c));
  }
 else if(e.getSource()==A.b6)
  { a=Double.valueOf(C.text1.getText()).doubleValue();
    c=Math.atan(a);
    D.text.setText(String.valueOf(c));
  }
 else if(e.getSource()==A.b7)
  { a=Double.valueOf(C.text1.getText()).doubleValue();
    b=Double.valueOf(C.text2.getText()).doubleValue();
    c=Math.pow(a,b);
    D.text.setText(String.valueOf(c));
  }
 else if(e.getSource()==A.b8)
  { a=Double.valueOf(C.text1.getText()).doubleValue();
    c=Math.abs(a);
    D.text.setText(String.valueOf(c));
  }
 else if(e.getSource()==A.b9)
  { a=Double.valueOf(C.text1.getText()).doubleValue();
    c=Math.sqrt(a);
    D.text.setText(String.valueOf(c));
  }
 else if(e.getSource()==A.b10)
  { a=Double.valueOf(C.text1.getText()).doubleValue();
    c=Math.exp(a);
    D.text.setText(String.valueOf(c));
  }
 else if(e.getSource()==A.b11)
  { a=Double.valueOf(C.text1.getText()).doubleValue();
    c=Math.log(a);
    D.text.setText(String.valueOf(c));
  }
 else if(e.getSource()==A.b12)
  { a=Double.valueOf(C.text1.getText()).doubleValue();
    b=Double.valueOf(C.text2.getText()).doubleValue();
    c=Math.max(a,b);
    D.text.setText(String.valueOf(c));
  }
 }
}



12-例子6
import java.applet.*;
import java.awt.*;
public class Example12_6 extends Applet
{ Label 编号,姓名,性别,出生,民族,学历,专业,籍贯,参加工作,住址,聘任,政治,业绩;
 TextField bianhao ,xingming,xingbie,chusheng,minzhu,xueli,zhuanye,
 jiguan,canjiagongzuo,zhuzhi,pinren,zhengzhi,yeji;
 Mypic  picture;     
 int x=0,y=0,w,h;
 public void init()
 { setLayout(null);
 编号=new Label("编号:",Label.CENTER);姓名=new Label("姓名:",Label.CENTER);
 性别=new Label("性别",Label.CENTER);
 出生=new Label("出生年月:",Label.CENTER);
 民族=new Label("民族:",Label.CENTER);
 学历=new Label("学历:",Label.CENTER);专业=new Label("专业:",Label.CENTER);
 籍贯=new Label("籍贯:",Label.CENTER);参加工作=new Label("参加工作时间:");
 住址=new Label("住址:",Label.CENTER); 聘任=new Label("聘任岗位:");
 政治=new Label("政治面貌:");业绩=new Label("业绩:",Label.CENTER); 
 bianhao=new TextField();xingming=new TextField();xingbie=new TextField();
 xingbie=new TextField();chusheng=new TextField();
 minzhu=new TextField();xueli=new TextField();
 zhuanye=new TextField();jiguan=new TextField();
 canjiagongzuo=new TextField();zhuzhi=new TextField();
 zhengzhi=new TextField(); pinren=new TextField();yeji=new TextField();
 picture=new Mypic();
 add(编号); add(姓名);add(性别);add(出生); add(民族);
 add(学历); add(专业);add(籍贯); add(参加工作);
 add(住址); add(聘任);add(政治);add(业绩); 
 add(bianhao);add(xingming);add(xingbie);
 add(xingbie);add(chusheng);
 add(minzhu);add(xueli);
 add(zhuanye);add(jiguan);
 add(canjiagongzuo);add(zhuzhi);add(pinren);
 add(zhengzhi);add(yeji);
 add(picture);
 w=getSize().width;h=getSize().height;//获取小程序的宽和高
 x=w/10;y=h/6;
 编号.setBounds(0,0,x,y);bianhao.setBounds(x,0,x,y);  
 姓名.setBounds(2*x,0,x,y);xingming.setBounds(3*x,0,x,y);
 性别.setBounds(4*x,0,x,y);xingbie.setBounds(5*x,0,x,y);
 出生.setBounds(6*x,0,x,y);chusheng.setBounds(7*x,0,x,y); 
 picture.setBounds(8*x,0,2*x,3*y);
 民族.setBounds(0,y,x,y);minzhu.setBounds(x,y,x,y);
 学历.setBounds(2*x,y,x,y); xueli.setBounds(3*x,y,x,y);
 专业.setBounds(4*x,y,x,y);zhuanye.setBounds(5*x,y,3*x,y);
 籍贯.setBounds(0,2*y,x,y);jiguan.setBounds(x,2*y,3*x,y); 
 参加工作.setBounds(4*x,2*y,2*x,y);canjiagongzuo.setBounds(6*x,2*y,2*x,y);
  住址.setBounds(0,3*y,x,y);zhuzhi.setBounds(x,3*y,3*x,y);
  聘任.setBounds(4*x,3*y,2*x,y);pinren.setBounds(6*x,3*y,4*x,y);
  政治.setBounds(0,4*y,x,2*y);zhengzhi.setBounds(x,4*y,2*x,2*y);
  业绩.setBounds(3*x,4*y,x,2*y);yeji.setBounds(4*x,4*y,6*x,2*y); 
 } 
}
class Mypic extends Canvas
{Mypic()
  {getSize();
  }
 public void paint(Graphics g)
 { g.setColor(Color.green);
   g.fillRect(0,0,50,50);//学习图象之后可在此处画照片（见二十二章）。
 }
  public Dimension getPreferredSize()
  {return new Dimension(160,100);   
  }
}