public class DB{
 public static return_type method(){
  //statement...
 }
}
interfere DBoperation{
abstract public return_type method();
abstract public return_type method(/*参数*/);

}
DB implement DBoperation{
//statement...
}

------解决方案--------------------
Java数据库操作类
package bean;
import java.sql.*;
public class Admin  
{
String DBDriver="sun.jdbc.odbc.JdbcOdbcDriver";
private Connection conn=null;
private Statement stmt=null;
ResultSet rs=null;
//修改DBUrl值可连接不同类型的数据库-ODBC/JDBC等等
public String DBUrl="jdbc:odbc:Driver={Microsoft Access Driver (*.mdb)};DBQ=";
public Admin(){
try{//注册
 Class.forName(DBDriver);
 }
    
catch(java.lang.ClassNotFoundException e)
{
System.err.println("出错啦！！数据库注册出毛病了！！！"+e.getMessage());
}
}
//输入为本地数据库（*.*.mdb相对路径）
public String getDataPath(String s)//非mdb数据库这个方法裁剪
{
 DBUrl =new String(DBUrl + s);
return DBUrl;
}
public ResultSet executeQuery(String sql)
{ rs=null;
try{//连接数据库查询
   conn=DriverManager.getConnection(DBUrl);
       //有密码的用conn=DriverManager.getConnection(DBUrl, ''用户名", "密码");
   stmt=conn.createStatement();
   rs=stmt.executeQuery(sql);
   }
 catch(SQLException ex)
 {
   System.err.println("暂时无法连接数据库！！"+ex.getMessage());
 }
 return rs;
}  
public ResultSet selectQuery()
{
 String sql = "select * from T_MIR";  
 rs=null;
 try{//连接数据库查询
     conn=DriverManager.getConnection(DBUrl);
       //有密码的用conn=DriverManager.getConnection(DBUrl, ''用户名", "密码");
     stmt=conn.createStatement();
       rs=stmt.executeQuery(sql);
     }
     catch(SQLException ex)
     {
         System.err.println("数据库查询出毛病了！！"+ex.getMessage());
     }
   return rs;
  
}
    
public void executeUpdate(String sql)
{
   stmt=null;
   rs=null;
 try{
     conn=DriverManager.getConnection(DBUrl);
       //有密码的用conn=DriverManager.getConnection(DBUrl, ''用户名", "密码");
     stmt=conn.createStatement();
     stmt.executeUpdate(sql);
     stmt.close();
     conn.close();
   }
 catch(SQLException ex)
 {
     System.err.println("暂时无法连接数据库！！"+ex.getMessage());  
 }
}
public void closeStmt()
{
 try{
       stmt.close();
   }
 catch(SQLException e)
 {
     e.printStackTrace();
 }
}
public void closeConn()
{
try{
     conn.close();
 }
catch(SQLException e)
   {
       e.printStackTrace();
   }
}