public class AA extends Applet {
  private int count = 0;
  private Button
    onOff = new Button("Toggle"),
    start = new Button("Start");
  private TextField t = new TextField(10);
  private boolean runFlag = true;
  public void init() {
    add(t);
    start.addActionListener(new StartL());
    add(start);
    onOff.addActionListener(new OnOffL());
    add(onOff);
  }
  public void go() {
    while (true) {
      try {
        Thread.currentThread().sleep(100);
      } catch (InterruptedException e){}
      if(runFlag)
        t.setText(Integer.toString(count++));
    }
  }
  class StartL implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      go();
    }
  }
  class OnOffL implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      runFlag = !runFlag;
    }
  }
  public static void main(String[] args) {
    AA applet = new AA();
    Frame aFrame = new Frame("AA");
    aFrame.addWindowListener(
      new WindowAdapter() {
        public void windowClosing(WindowEvent e) {
          System.exit(0);
        }
      });
    aFrame.add(applet, BorderLayout.CENTER);
    aFrame.setSize(300,200);
    applet.init();
    applet.start();
    aFrame.setVisible(true);
  }
} ///:~


2�br />class SuperClass
{
 int a = 3,b = 6;}
class SubClass extends SuperClass
{
// int a=30,b=20;
 int max(){return ((a > b)? a:b);}}
public class ABC {

 public static void main(String[] args) {
 SubClass sb = new SubClass();
 System.out.println(sb.max());

 }

}


3.
   interface  Playable   {
       void  play();
  }
    interface  Bounceable   {
       void  play();
  }
    interface  Rollable  extends  Playable, Bounceable   {
      Ball ball  =   new  Ball( " PingPang " );//interface 里面的变量äØ“public static final
  }
    class  Ball  implements  Rollable   {
       private  String name;
        public  String getName()   {
           return  name;
      }
        public  Ball(String name)   {
          this .name  =  name;       
      }
      public   void  play()   {
//          ball  =   new  Ball( " Football " );
          System.out.println(ball.getName());
      }
  }


4.
public class BB {
 String a ;
public BB(String a){
 this.a = a;
 System.out.println("11");
}
 public static void main(String[] args) {
  String s = new String ("Computer");
  if(s == "Computer")
   System.out.println("Equal A");
  if(s.equals("Computer"))
   System.out.println("Equal B");
  BB b = new BB("aa");
  BB c = new BB("aa");
  BB d ;
  d = c;
  
  if(b == c)
   System.out.println("Equal b=c");
  if(b.equals("aa"))
   System.out.println("Equal b equals 'aa'");
  if(d.equals("aa"))
   System.out.println("Equal d equals 'aa'");
  if(d.equals(c))
   System.out.println("Equal d equals 'c'");
  if(d==c)
   System.out.println("Equal d equals 'c'");

 }

}


5.

interface  A{
    int x = 0;
 }
 class B{
    int x =1;
 }
 class C extends B implements A {
    public void pX(){
//       System.out.println(x);//两个x都匹é…?对于父类的变é‡?可以用super.x来明¼‹®ï¼Œè€ŒæŽ¥å£çš„属性默认隐含äØ“ public static final.所以可以通过A.x来明¼‹®ã€?/p>

    }
    public static void main(String[] args) {
       new C().pX();
    }
 }


6.
public class CalC {
     void amethod(){
        System.out.println("CalC.amethod");
      }
      CalC(){//---------�
         amethod();//----�
          System.out.println("Hu?");
     }
     public static void main(String[] args) {
         // TODO Auto-generated method stub
         CalC cc = new CalChild();//--1初始化调用构造方法，向上转型åQŒè°ƒç”¨å¼—é›ähž„造方æ³?br />         System.out.println("1");
         cc.amethod();
     }
 }
 class CalChild extends CalC{
  //----2
     void amethod(){//-----5
        System.out.println("CalChild.amethod");
    }
 }


7.
class Vehicle{
 String str;
 public Vehicle(){}
 public Vehicle(String s){
  
 }
}
 public class Car {
 String a;
  public Car(String a){this.a = a;}
 public static void main(String[] args) {
   Vehicle v = new Vehicle("Hello");
   Car a;
//   a = "a";
  v = new Vehicle ("How are You");
  v.str = "How is going";
  System.out.println("Greeting is :" + v+"11");
 }

}


8.
class  Parent{
 private void method1(){
  System.out.println("Parent's method1()");
 }
 public void method2(){
  System.out.println("Parent's method2()");
  method1();
 }
}
public class Childe extends Parent {
 public void method1(){
  System.out.println("Child's method1()");
 }
 
 public static void main(String[] args) {
 Parent p = new Childe();
 p.method2();

 }

}         


9.
class   O   {  
        public   O()   {  
           System.out.println("A's   c   is   here   ");  
      }  
       void   println()  {  
           System.out.println("A's   v   is   here   ");  
       }  
    }  
 class   P   extends  O {  
       public   P()   {  
           System.out.println("B's   c   is   here   ");  
       }  
       void   println()  {  
           System.out.println("B's   v   is   here   ");  
       }  
   }  
   public   class   Chp_4_2  {  
       public   static   void   main(String[]   args)  {  
           O   b   =   new   P();
           b.println();
       }  
  }

10.
public class Cwich {

 /**
  * @param args
  */
 public static void main(String[] args) {
  int x = 9;
  switch(x){
  default:
   System.out.println(1);
  case 1:
  System.out.println(1);
  case 2:
  case 3:
   System.out.println(3);break;
  case 4:
   System.out.println("4");
//  default:
//   break;
  }


11.
class Tree{}
class Pine extends Tree{}
class Oak extends Tree{}
public class Forest {

 public static void main(String[] args) {
  
  Tree tree = new Pine();
  if(tree instanceof Pine)
   System.out.println("Pine");
  if(tree instanceof Tree)
   System.out.println("Tree");
  if(tree instanceof Oak)
   System.out.println("Oak");
  else
   System.out.println("Oops");

 }

}



12.
class FuZhia {
  private int a;
   public int change(int m) {
     return m;  
   } 
   
 }
 public class FuZhi extends FuZhia{
   public int b; 
  public static void main() {
   FuZhi  aa = new FuZhi();
   FuZhia  bb = new FuZhia();
    int k; 
    k=bb.change(30); 
   }
 }

13.
import java.sql.*;
public class Jdbc
{
String dbUrl="jdbc:oracle:thin:@127.0.0.1:1521:orcl";
String theUser="admin";
String thePw="manager";
Connection c=null;
Statement conn;
ResultSet rs=null;
public Jdbc()
{
try{
Class.forName("oracle.jdbc.driver.OracleDriver").newInstance();
c = DriverManager.getConnection(dbUrl,theUser,thePw);
conn=c.createStatement();
}catch(Exception e){
e.printStackTrace();
}
}
public boolean executeUpdate(String sql)
{
try
{
conn.executeUpdate(sql);
return true;
}
catch (SQLException e)
{
e.printStackTrace();
return false;
}
}
public ResultSet executeQuery(String sql)
{
rs=null;
try
{
rs=conn.executeQuery(sql);
}
catch (SQLException e)
{
e.printStackTrace();
}
return rs;
}
public void close()
{
try
{
conn.close();
c.close();
}
catch (Exception e)
{
e.printStackTrace();
}
}
public static void main(String[] args)
{
ResultSet rs;
Jdbc conn = new Jdbc();
rs=conn.executeQuery("select * from test");
try{
while (rs.next())
{
System.out.println(rs.getString("id"));
System.out.println(rs.getString("name"));
}
}catch(Exception e)
{
e.printStackTrace();
}
}
}

14.
class AB {
 String s1;
 String s2;
 AB(String str1,String str2){
  s1 = str1;s2 = str2;
 }
 public String toString(){
  return s1+s2;
 }
}
public class jiahao {
 public static void main(String[] args) {
  AB s = new AB("Hello!","I love Java.");
  System.out.println(s.toString());
 }

}


15.
class N{
 N(){
  System.out.println("Class N Constructor");
 }
}
public class M extends N{
 M(){System.out.println("Class M Constructor");}
 
 public static void main(String[] args) {
  M m = new M();

 }

}


16.
   class  Base  {
         private  final  void  f()  {  //注意final
           System.out.println( " Base.f() " );
//           public int i;//局部变量前不能攄¡½®ä»ÖM½•ä¿®é¥°½W?br />       }
   }
  
    class  Derived  extends  Base  {
         public  final  void  f()  {   //注意final
          System.out.println( " Derived.f() " );
      }
  }
  
    public   class  Main   {
            public   static   void  main(String[] args)   {
          Derived op1  =   new  Derived();
         Base op2 = op1;
          op1.f();
//         op2.f();
      }
 }



17.
import java.awt.AWTEvent;
import java.awt.TextArea;
import java.awt.event.TextEvent;

public class MyTextArea extends TextArea{
 public MyTextArea(int nrows,int ncols){
  enableEvents(AWTEvent.TEXT_EVENT_MASK);
 }

 public void processTextEvent(TextEvent te){
  System.out.println("Processing a text event.");
 }
}


18.
public class Outer {
 final String s = "i am outer class member variable";
 public void Method(){
  String s1 = "i am inner class variable";
  class InnerClass{
   String s2 = "i am inner class variable";
   public void innerMethod(){
    int xyz = 20;
    System.out.println(s);
    System.out.println("Integer value is " + xyz);
    System.out.println(s2);
   }
  }
 }
 public static void main(String[] args) {
  // TODO Auto-generated method stub

 }

}



19.
public class Outerclass

{

private class InterClass

{

public InterClass()

{

System.out.println("InterClass Create");

}

}

public Outerclass()

{

InterClass ic = new InterClass();

System.out.println("OuterClass Create");

}

public static void main(String[] args)

{

Outerclass oc = new Outerclass();

}

}



20.
public class Parent1 {
  public void test(){ }
  public Parent1(){
         test();
    }
  public static void main(String[] args){
         new Child1();
     }
}

class Child1 extends Parent1{
        public int instanceValue = 20;
        public Child1(){
              //super();
              System.out.println("instance value isa: " + instanceValue);
          }
    public void test(){
            System.out.println("instance value is: " + instanceValue);
       }
  }