一个类无法调用另一个类

[chensugang]

例如:已经有DBConnection.java( 都是public 定义的)
我的在Login.java中调用它不好用.这是为什么啊?

[tlowl]

大哥，你能不能有点专业精神啊？光这么说谁知道是怎么回事啊，把代码贴出来！！

[chensugang]

package caiwu;

import java.sql.*;

public class DBConnection
{
private Connection conn=null;
private Statement stmt=null;
private ResultSet rs =null;

public void DBConnection(){
try{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
conn=DriverManager.getConnection("jdbc:odbc:caiwu");
}
catch(ClassNotFoundException e){
}
catch(SQLException se){
}
}
public ResultSet myquery(String stringquery) throws SQLException{

stmt=conn.createStatement();
rs=stmt.executeQuery(stringquery);
return rs;

}
public void dbclose() throws SQLException{
stmt.close();
conn.close();
}
}


package caiwu;

import java.sql.*;
import java.util.*;

public class LoginMaster extends Master{

public boolean ismaster;

public ResultSet rs;

public LoginMaster(){};

public boolean CheckLogin() throws Exception {
DBConnection dbconnection = null;
try{
dbconnection = new DBConnection();
rs=dbconnection.myquery("select * from master where name='"+userName.getBytes("GB2312")+"' and pass='"+userPassword.getBytes("GB2312")+"'");
if(!rs.next()){
ismaster = false;
}else{
ismaster = true;
}
}catch(Exception e){
System.err.println(e);
}finally{
try{
dbconnection.dbclose();
}catch(Exception e){
e.printStackTrace();
}
}
return ismaster;
}
}

[chensugang]

LoginMaster.java:15: cannot resolve symbo
symbol : class DBConnection
location: class caiwu.LoginMaster
DBConnection dbconnection = null;

[chensugang]

谢谢

[zcjl]

javac -d . *.java

[chengys]

ding

[tlowl]

老兄拜托你把Master类也贴出来！

[terry_yip]

dbconnection = new DBConnection();

应为DBConnection dbconnection = new DBConnection();

还有，把
public void DBConnection(){
try{

这里的void去掉，构造函数不能用void不修饰。

[zhouqi724]

在DBConnection里重写个方法，把连接数据库放到那个方法里去
不用新建类实例，直接用类.方法调用，效率更好
对象尽量要少

[suyejun2005]

在Login里面要import caiwu.DBConnect;