日期:2014-05-18  浏览次数:20756 次

请教:同一包中类的继承问题
一个文件中的类继承另一个文件中的类,但两个文件在同一个自定义的包中, 
没有用import的时候说找不到所继承的类,写了个Import语句似乎又是错误的,不知道该怎么改? 
程序如下: 
dbcon.java 

package beans; 
import java.sql.*; 
public class dbcon 

Connection con; 
public dbcon() 



public Connection getConnection() 

try 

Class.forName("sun.jdbc.odbc.JdbcOdbcDriver"); 
con=DriverManager.getConnection("jdbc:odbc:shopdb","",""); 

catch (Exception e) 

System.out.println(e.toString()); 
con=null; 

return con; 

}; 

dbexecute.java 

package beans; 
import java.sql.*; 
public class dbexecute extends dbcon 

private Connection con; 
private Statement sql; 
private ResultSet rs; 

public dbexecute() 

con=super.getConnection(); 
sql=null; 
rs=null; 


public boolean exeUpdate(String sqlstr) //执行更新操作 

try 

sql=con.createStatement(); 
sql.executeUpdate(sqlstr); 
return true; 

catch (Exception e) 

System.out.println(e.toString()); 
return false; 



public ResultSet exeQuery(String sqlstr) //执行查询操作 

try 

sql=con.createStatement(); 
rs=sql.executeQuery(sqlstr); 

catch (Exception e) 

System.out.println(e.toString()); 
  rs=null; 

return rs; 



错误提示: 

E:\JSP\myshop\WEB-INF\classes\beans>javac dbexecute.java 
dbexecute.java:5: cannot find symbol 
symbol: class dbcon 
public class dbexecute extends dbcon 
  ^ 
dbexecute.java:13: cannot find symbol 
symbol : variable super 
location: class beans.dbexecute 
  con=super.getConnection(); 
  ^ 
2 errors 

E:\JSP\myshop\WEB-INF\classes\beans>


------解决方案--------------------
E:\JSP\myshop\WEB-INF\classes\beans>javac dbcon.java 生成dbcon.class

然后 

E:\JSP\myshop\WEB-INF\classes\beans>javac -classpath E:\JSP\myshop\WEB-INF\classes dbexecute.java 生成dbexecute.class