java工厂模式

1.定义接口类IDaoUser

public interface IDaoUser {
 public String getSql_maxusrno();
} 

2.定义工厂类，此工厂类实现了两个不同类的调用。

public final class DaoUserFactory {
 
 public static IDaoUser getInstance(int dbtype)
 {
  switch (dbtype)
  {
   case 1:  //for sqlserver
    return new DaoUserForSqlServer();
   case 2:  //for oracle
    return new DaoUserForOracle();
  }
  return null;
 }

}

3、接口的实现，实现了接口IDaoUser的方法

public class DaoUser implements IDaoUser {

 public String getSql_maxusrno() {
  // TODO Auto-generated method stub
   return "select max(to_number(usrno)) from data_user";
 }

}

4、继承类的实现

工厂中如果选择case 2 则调用DaoUserForOracle 类

public class DaoUserForOracle extends DaoUser{

}

工厂中如果选择case 1 则调用DaoUserForSqlServer 类

public class DaoUserForSqlServer extends DaoUser {

}