通过实例可以更好的了解java

   if(i%4==0)         {b[i].setBounds(k1,40,30,30);k1=k1+31;}
   else if(i%4==1)  {b[i].setBounds(k2,71,30,30);k2=k2+31;}
   else if(i%4==2)  {b[i].setBounds(k3,102,30,30);k3=k3+31;}
   else if(i%4==3)  {b[i].setBounds(k4,133,30,30);k4=k4+31;}
  }
  for(int i=0;i<40;i++)
  { x[i]=b[i].getBounds().x;y[i]=b[i].getBounds().y;//获取按钮左上角的x,y坐标。
  }
 }
 public void keyTyped(KeyEvent e)
 { } 
 public void keyPressed(KeyEvent e)
 {if(e.getKeyCode()==KeyEvent.VK_UP)
    {for(int i=0;i<=39;i++)
      { if(s.equals(String.valueOf(i)))
        {y[i]=y[i]-2;
         if(y[i]<=0) y[i]=0;
         b[i].setLocation(x[i],y[i]);
        }
      }
    }
 else if(e.getKeyCode()==KeyEvent.VK_DOWN)
    {for(int i=0;i<=39;i++)
      {if(s.equals(String.valueOf(i)))
        {y[i]=y[i]+2;
        if(y[i]>=300) y[i]=300;
        b[i].setLocation(x[i],y[i]); 
        }
      }
    }
 else if(e.getKeyCode()==KeyEvent.VK_LEFT)
    {for(int i=0;i<=39;i++)
      {if(s.equals(String.valueOf(i)))
       {x[i]=x[i]-2;
        if(x[i]<=0) x[i]=0;
        b[i].setLocation(x[i],y[i]);
       }
      }
    } 
 else if(e.getKeyCode()==KeyEvent.VK_RIGHT)
    {for(int i=0;i<=39;i++)
      {if(s.equals(String.valueOf(i)))
       {x[i]=x[i]+2;
        if(x[i]>=300) x[i]=300;
        b[i].setLocation(x[i],y[i]);
       }
      }
    }
  
 }
 public void keyReleased(KeyEvent e)
 {}
 public void actionPerformed(ActionEvent e)
 { for(int i=0;i<40;i++)
   {if(e.getSource()==b[i])
     s=b[i].getLabel();
   }
 }
}　　



18-例子14
import java.applet.*;import java.awt.*;
import java.awt.event.*;
public class Example18_14 extends Applet 
implements ActionListener,KeyListener
{TextField text=new TextField(10);Label label=null;
Button button=new Button("确定");
public void init()
 {text.addKeyListener(this);//获得处理键盘事件的监视器。
  button.addActionListener(this);
  label=new Label("输入一个数后点击按扭：");
  add(label); add(text);add(button);
 }
public void actionPerformed(ActionEvent e)
 {double a=0;
  a=Double.valueOf(text.getText()).doubleValue();
  text.setText(""+Math.sqrt(a)); 
 }
 public void keyPressed(KeyEvent e)
 {label.setBackground(Color.green);
  char c=e.getKeyChar();
  boolean b1=(c<'0'||c>'9'),
          b2=(c!='.'),
          b3=(c!=KeyEvent.VK_BACK_SPACE);
  if(b1&&b2&&b3)  //判断是否输入了非数字字符。
   {label.setBackground(Color.red);
text.setText(text.getText().substring(0,text.getText().indexOf(c)));
   } 
}
public void keyTyped(KeyEvent e)
 {}
public void keyReleased(KeyEvent e)
 {}
}



18-例子15

import java.awt.*;import java.awt.event.*;
//创建棋盘的类：
class ChessPad extends Panel  implements MouseListener,ActionListener
{  int x=-1,y=-1, 棋子颜色=1;               //控制棋子颜色的成员变量。
   Button button=new Button("重新开局");    //控制重新开局的按扭。
   TextField text_1=new TextField("请黑棋下子"),
             text_2=new TextField();              //提示下棋的两个文本框。
  ChessPad()
  {setSize(440,440);
   setLayout(null);setBackground(Color.pink);
   addMouseListener(this);add(button);button.setBounds(10,5,60,26);
   button.addActionListener(this);
   add(text_1);text_1.setBounds(90,5,90,24);
   add(text_2);text_2.setBounds(290,5,90,24);
   text_1.setEditable(false);text_2.setEditable(false);
  }
 public void paint(Graphics g)                    //绘制围棋棋盘的外观。
  {for(int i=40;i<=380;i=i+20)
    {g.drawLine(40,i,400,i);}
     g.drawLine(40,400,400,400);
   for(int j=40;j<=380;j=j+20)
    {g.drawLine(j,40,j,400);}
     g.drawLine(400,40,400,400); 
     g.fillOval(97,97,6,6); g.fillOval(337,97,6,6);
     g.fillOval(97,337,6,6);g.fillOval(337,337,6,6);
     g.fillOval(217,217,6,6);
  }
 public void mousePressed(MouseEvent e)     //当按下鼠标左键时下棋子。
  { if(e.getModifiers()==InputEvent.BUTTON1_MASK)
    { x=(int)e.getX();y=(int)e.getY();      //获取按下鼠标时的坐标位置。
      ChessPoint_black chesspoint_black=new ChessPoint_black(this);
      ChessPoint_white chesspoint_white=new ChessPoint_white(this);
      int a=(x+10)/20,b=(y+10)/20;
     if(x/20<2||y/20<2||x/20>19||y/20>19)    //棋盘以外不下棋子。
         {}
     else{ if(棋子颜色==1)                       //当棋子颜色是1时下黑棋子。
          {this.add(chesspoint_black);
           chesspoint_black.setBounds(a*20-7,b*20-7,16,16);
           棋子颜色=棋子颜色*(-1);             
           text_2.setText("请白棋下子");
           text_1.setText("");
          }
         else if(棋子颜色==-1)                   //当棋子颜色是-1时下白棋子。
          {this.add(chesspoint_white);
           chesspoint_white.setBounds(a*20-7,b*20-7,16,16);
           棋子颜色=棋子颜色*(-1);
           text_1.setText("请黑棋下子");
           text_2.setText("");
          }
        }
    }
  }
 public void mouseReleased(MouseEvent e){}
 public void mouseEntered(MouseEvent e) {}
 public void mouseExited(MouseEvent e) {}
 public void mouseClicked(MouseEvent e){}
 public void actionPerformed(ActionEvent e)
 {this.removeAll();棋子颜色=1;
  add(button);button.setBounds(10,5,60,26);
  add(text_1);text_1.setBounds(90,5,90,24);  
  text_2.setText("");text_1.setText("请黑棋下子");
  add(text_2);text_2.setBounds(290,5,90,24);
 }
}
//负责创建黑色棋子的类：
class ChessPoint_black extends Canvas implements MouseListener
{ ChessPad chesspad=null;                        //棋子所在的棋盘。
 ChessPoint_black(ChessPad p)
  {setSize(20,20);chesspad=p; addMouseListener(this);
  }
 public void paint(Graphics g)                    //绘制棋子的大小。
  { g.setColor(Color.black);g.fillOval(0,0,14,14);
  } 
 public void mousePressed(MouseEvent e) 
 { if(e.getModifiers()==InputEvent.BUTTON3_MASK)
   {chesspad.remove(this);//当用鼠标右键点击棋子时，从棋盘中去掉该棋子（悔棋）。
    chesspad.棋子颜色=1;
    chesspad.text_2.setText("");chesspad.text_1.setText("请黑棋下子");
   }
 }
 public void mouseReleased(MouseEvent e){}
 public void mouseEntered(MouseEvent e) {}
 public void mouseExited(MouseEvent e) {}
 public void mouseClicked(MouseEvent e)
 { if(e.getClickCount()>=2)
  chesspad.remove(this);             //当用左键双击该棋子时，吃掉该棋子。
 }
}
//负责创建白色棋子的类：
class ChessPoint_white extends Canvas implements MouseListener
{  
  ChessPad chesspad=null;
  ChessPoint_white(ChessPad p)
  {setSize(20,20);addMouseListener(this);
   chesspad=p; 
  }
 public void paint(Graphics g)
  { g.setColor(Color.white);g.fillOval(0,0,14,14); 
  } 
 public void mousePressed(MouseEvent e)
 { if(e.getModifiers()==InputEvent.BUTTON3_MASK)
   {chesspad.remove(this);chesspad.棋子颜色=-1;
    chesspad.text_2.setText("请白棋下子"); chesspad.text_1.setText("");
   }
 }
 public void mouseReleased(MouseEvent e){}
 public void mouseEntered(MouseEvent e) {}
 public void mouseExited(MouseEvent e) {}
 public void mouseClicked(MouseEvent e)
 {if(e.getClickCount()>=2)
  chesspad.remove(this);
 }
}
public class Chess extends Frame  //添加棋盘的窗口。
{ChessPad chesspad=new ChessPad();
  Chess()
 {setSize(600,600);
  setVisible(true);
  setLayout(null);
  Label label=
new Label("单击下棋子，双击吃棋子，右击棋子悔棋",Label.CENTER);
  add(label);label.setBounds(70,55,440,26);
  label.setBackground(Color.orange); 
  add(chesspad);chesspad.setBounds(70,90,440,440);
  addWindowListener(new WindowAdapter()
    {public void windowClosing(WindowEvent e){System.exit(0);}
    });
  }
public static void main(String args[])
 { Chess chess=new Chess();
 }
}



18-例子16
import java.awt.event.*;import java.applet.*;
import java.awt.*;
public class Move extends.Applet implements KeyListener,ActionListener
{ Button b_go=new Button("go"),
         b_replay=new Button("replay");
  Rectangle rect1,rect2,rect3;
  int b_x=0,b_y=0;
  public void init()
  {b_go.addKeyListener(this);
   b_replay.addActionListener(this);
   setLayout(null);
   //代表迷宫的矩形：
    rect1=new Rectangle(20,40,200,40);
    rect2=new Rectangle(200,40,24,240);
    rect3=new Rectangle(200,220,100,40);
    b_go.setBackground(Color.red);      //代表走迷宫者的按扭。 
    add(b_go);b_go.setBounds(22,45,20,20);
    b_x=b_go.getBounds().x;b_y=b_go.getBounds().y;
     b_go.requestFocus() ;
    add(b_replay);b_replay.setBounds(2,2,45,16);//点击重新开始的按扭。   
  }
  public void paint(Graphics g)
  { //画出迷宫：
    g.setColor(Color.green);
    g.fillRect(20,40,200,40);
    g.setColor(Color.yellow);
    g.fillRect(200,40,40,240);
    g.setColor(Color.cyan);
    g.fillRect(200,220,100,40);
    g.drawString("出口",310,220);
    g.setColor(Color.black);
    g.drawString("点击红色按扭，然后用键盘上的方向键移动按扭",100,20);
  }
 public void keyPressed(KeyEvent e)
 { //按键盘上的上下、左右键在迷宫中行走：
  if((e.getKeyCode()==KeyEvent.VK_UP))
    { //创建一个和按扭：b_go 同样大小的矩形：
      Rectangle rect=new Rectangle(b_x,b_y,20,20);
      //要求必须在迷宫内行走：
      if(rect.intersects(rect1)||rect.intersects(rect2)||
rect.intersects(rect3))
        {b_y=b_y-2;b_go.setLocation(b_x,b_y);}
    }
 else if(e.getKeyCode()==KeyEvent.VK_DOWN)
    { Rectangle rect=new Rectangle(b_x,b_y,20,20);
      if(rect.intersects(rect1)||rect.intersects(rect2)||
rect.intersects(rect3))
       { b_y=b_y+2;b_go.setLocation(b_x,b_y);}
    }
 else if(e.getKeyCode()==KeyEvent.VK_LEFT)
    {  Rectangle rect=new Rectangle(b_x,b_y,20,20);
      if(rect.intersects(rect1)||rect.intersects(rect2)
||rect.intersects(rect3))
         {b_x=b_x-2;b_go.setLocation(b_x,b_y);} 
    } 
 else if(e.getKeyCode()==KeyEvent.VK_RIGHT)
    { Rectangle rect=new Rectangle(b_x,b_y,20,20);
      if(rect.intersects(rect1)||rect.intersects(rect2)||
rect.intersects(rect3))
        { b_x=b_x+2;b_go.setLocation(b_x,b_y);}
    }
 }
 public void keyReleased(KeyEvent e){}
  public void keyTyped(KeyEvent e){}
 public void actionPerformed(ActionEvent e)
  { b_go.setBounds(22,45,20,20); 
b_x=b_go.getBounds().x;b_y=b_go.getBounds().y;
b_go.requestFocus() ;
} 
}



18-例子17
import java.awt.*;
import java.applet.*;
import java.awt.event.*;
class People extends Button implements FocusListener //代表华容道人物的类。
{Rectangle rect=null;
int left_x,left_y;//按扭的左上角坐标.
int width,height; //按扭的宽和高.
String name; int number;
People(int number,String s,int x,int y,int w,int h,Hua_Rong_Road road)
   {super(s);
  name=s;this.number=number;
  left_x=x;left_y=y;
  width=w;height=h;  setBackground(Color.orange);
  road.add(this);    addKeyListener(road);
  setBounds(x,y,w,h);addFocusListener(this);
  rect=new Rectangle(x,y,w,h);
 }
 public void focusGained(FocusEvent e)
   { setBackground(Color.red);
   }
 public void focusLost(FocusEvent e)
   { setBackground(Color.orange);
   }
}
public class Hua_Rong_Road extends Applet
 implements KeyListener,ActionListener
{   People people[]=new People[10];
    Rectangle left,right,above ,below;//华容道的边界 .
    Button restart=new Button("重新开始");   
  public void init()
  {setLayout(null); add(restart);
   restart.setBounds(5,5,80,25);
   restart.addActionListener(this);
   people[0]=new People(0,"曹操",104,54,100,100,this); 
   people[1]=new People(1,"关羽",104,154,100,50,this); 
   people[2]=new People(2,"张飞",54, 154,50,100,this); 
   people[3]=new People(3,"刘备",204,154,50,100,this); 
   people[4]=new People(4,"张辽",54, 54, 50,100,this); 
   people[5]=new People(5,"曹仁",204, 54, 50,100,this);  
   people[6]=new People(6,"兵  ",54,254,50,50,this);  
   people[7]=new People(7,"兵  ",204,254,50,50,this); 
   people[8]=new People(8,"兵  ",104,204,50,50,this); 
   people[9]=new People(9,"兵  ",154,204,50,50,this); 
   people[9].requestFocus();
   left=new Rectangle(49,49,5,260);
 people[0].setForeground(Color.white) ;   
   right=new Rectangle(254,49,5,260);
   above=new Rectangle(49,49,210,5);
   below=new Rectangle(49,304,210,5);
 }
 public void paint(Graphics g)
    {//画出华容道的边界:
      g.setColor(Color.cyan);
      g.fillRect(49,49,5,260);//left.
      g.fillRect(254,49,5,260);//right.
      g.fillRect(49,49,210,5); //above.
      g.fillRect(49,304,210,5);//below.
    //提示曹操逃出位置和按键规则:
      g.drawString("点击相应的人物,然后按键盘上的上下左右箭头移动",100,20);
      g.setColor(Color.red);
      g.drawString("曹操到达该位置",110,300);
    }
 public void keyPressed(KeyEvent e) 
    { People man=(People)e.getSource();//获取事件源.
      man.rect.setLocation(man.getBounds().x, man.getBounds().y);
      if(e.getKeyCode()==KeyEvent.VK_DOWN)
        {             man.left_y=man.left_y+50;     //向下前进50个单位。
                      man.setLocation(man.left_x,man.left_y);
                      man.rect.setLocation(man.left_x,man.left_y);
        //判断是否和其它人物或下边界出现重叠,如果出现重叠就退回50个单位距离。       
        for(int i=0;i<10;i++)
            {if((man.rect.intersects(people[i].rect))&&(man.number!=i))
                    {man.left_y=man.left_y-50;
                     man.setLocation(man.left_x,man.left_y);
                     man.rect.setLocation(man.left_x,man.left_y);   
                    }
             }
      if(man.rect.intersects(below))
            { man.left_y=man.left_y-50;
             man.setLocation(man.left_x,man.left_y);
             man.rect.setLocation(man.left_x,man.left_y); 
            } 
       }
   if(e.getKeyCode()==KeyEvent.VK_UP)
     {  man.left_y=man.left_y-50;     //向上前进50个单位。
        man.setLocation(man.left_x,man.left_y);
        man.rect.setLocation(man.left_x,man.left_y);
        //判断是否和其它人物或上边界出现重叠,如果出现重叠就退回50个单位距离。 
        for(int i=0;i<10;i++)
            {if((man.rect.intersects(people[i].rect))&&(man.number!=i))
                    {man.left_y=man.left_y+50;
                     man.setLocation(man.left_x,man.left_y);
                     man.rect.setLocation(man.left_x,man.left_y);   
                    }
             }
        if(man.rect.intersects(above))
            { man.left_y=man.left_y+50;
             man.setLocation(man.left_x,man.left_y);
             man.rect.setLocation(man.left_x,man.left_y); 
            } 
       }
    if(e.getKeyCode()==KeyEvent.VK_LEFT)
       {man.left_x=man.left_x-50;     //向左前进50个单位。
        man.setLocation(man.left_x,man.left_y);
        man.rect.setLocation(man.left_x,man.left_y);
        //判断是否和其它人物或左边界出现重叠,如果出现重叠就退回50个单位距离。
        for(int i=0;i<10;i++)
            {if((man.rect.intersects(people[i].rect))&&(man.number!=i))
                    {man.left_x=man.left_x+50;
                     man.setLocation(man.left_x,man.left_y);
                     man.rect.setLocation(man.left_x,man.left_y);   
                    }
             }
        if(man.rect.intersects(left))
            { man.left_x=man.left_x+50;
             man.setLocation(man.left_x,man.left_y);
             man.rect.setLocation(man.left_x,man.left_y); 
            } 
       }
   if(e.getKeyCode()==KeyEvent.VK_RIGHT)
     {  man.left_x=man.left_x+50;     //向右前进50个单位。
        man.setLocation(man.left_x,man.left_y);
        man.rect.setLocation(man.left_x,man.left_y);
        //判断是否和其它人物或右边界出现重叠,如果出现重叠就退回50个单位距离。
        for(int i=0;i<10;i++)
            {if((man.rect.intersects(people[i].rect))&&(man.number!=i))
                    {man.left_x=man.left_x-50;
                     man.setLocation(man.left_x,man.left_y);
                     man.rect.setLocation(man.left_x,man.left_y);   
                    }
             }
        if(man.rect.intersects(right))
            { man.left_x=man.left_x-50;
             man.setLocation(man.left_x,man.left_y);
             man.rect.setLocation(man.left_x,man.left_y); 
            } 
       }
 }
 public void keyTyped(KeyEvent e){}
 public void keyReleased(KeyEvent e){}
 public void actionPerformed(ActionEvent e)
 { this.removeAll();
   this.init();
 } 
}