TOMCAT,SERVLET,在一个自己写的类A 里调用另一个已经编译过的类B，编译出错

[zzzjaychung]

目的：在一个自己写的类A 里调用另一个已经编译过的类B。A和B在同一个目录下。使用TOMCAT。
在编译类A的时候出错，刚刚看JAVA三天，现在还有点搞不清晨面的关系，请大侠们帮忙看看。


编译类A时出错信息：

C:\Documents and Settings\Shaun>javac C:\jakarta-tomcat\webapps\Assignment1\WEB-
INF\classes\mypack\ShowBalance.java
C:\jakarta-tomcat\webapps\Assignment1\WEB-INF\classes\mypack\ShowBalance.java:47
: cannot resolve symbol
symbol  : class BankCustomer
location: class mypack.ShowBalance
                        BankCustomer bc = new BankCustomer(userid, username, bal
ance, level);
                        ^
C:\jakarta-tomcat\webapps\Assignment1\WEB-INF\classes\mypack\ShowBalance.java:47
: cannot resolve symbol
symbol  : class BankCustomer
location: class mypack.ShowBalance
                        BankCustomer bc = new BankCustomer(userid, username, bal
ance, level);
                                              ^
2 errors

类A的代码：

package mypack;

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

public class ShowBalance {	
	public ShowBalance(String UserName)
		throws IOException{					
			
		try{

			String clientName = UserName;
			
			//connect to database
			String dbUrl = "jdbc:mysql://localhost:3306/balancecontrol";
			String dbUser = "Jay";
			String dbPwd = "123456";
			
			//load driver
			Class.forName("com.mysql.jdbc.Driver");
			//regesister driver
			java.sql.DriverManager.registerDriver(new com.mysql.jdbc.Driver());
						
			Connection con = java.sql.DriverManager.getConnection(dbUrl,dbUser,dbPwd);
			Statement stmt = con.createStatement();
			
			String sql = "select user_id, user_name, balance, level from user_balance where user_name = '" + clientName + "' ";
			ResultSet rs = stmt.executeQuery(sql); 			
			
			int userid = 1000;
			String username = "New Customer";
			float balance = 0;
			int level = 3;				
			
			if(rs.next()){
				userid = rs.getInt("user_id");
				username = rs.getString("user_name");
				balance = rs.getFloat("balance");
				level = rs.getInt("level");												
			}
			
			rs.close();
			stmt.close();
			con.close();	
			
			BankCustomer bc = new BankCustomer(userid, username, balance, level);
			
		}
		
		catch(Exception e){
			throw new IOException(e.getMessage());
		}
	}
    
}

类B的代码：

package mypack;

public class BankCustomer{

	private int userid = 1000;
	private String username = "New Customer";
	private float balance = 0;
	private int level = 3;
	
	public void Bankcustomer(int userid, String username, float balance, int level){
		this.userid = userid;
		this.username = username;
		this.balance = balance;
		this.level = level;	
	}
	
	public int getUserID(){
		return userid;
	}

	public String getUserName(){
		return username;
	}

	public float getBalance(){
		return balance;
	}
	
	public int getLevel(){
		return level;
	}	
}

[zzzjaychung]

各位大侠，急啊。谁给看看。谢谢。

[jz1979]

在BankCustomer里把

 public void Bankcustomer(int userid, String username, float balance, int level){
        this.userid = userid;
        this.username = username;
        this.balance = balance;
        this.level = level;    
}

改成

 public void Bankcustomer(int userid1, String username1, float balance1, int level1){
        this.userid = userid1;
        this.username = username1;
        this.balance = balance1;
        this.level = level1;    
 }

注意形参名不要与本身变量名相同

[jz1979]

不好意思,刚才的错了
应该是

public Bankcustomer(int userid, String username, float balance, int level){
        this.userid = userid;
        this.username = username;
        this.balance = balance;
        this.level = level;    
}

[jz1979]

构造函数不能有返回值

[jz1979]

还有注意大小写,构造函数名与类名相同

public BankCustomer(int userid, String username, float balance, int level){
        this.userid = userid;
        this.username = username;
        this.balance = balance;
        this.level = level;    
}

[zzzjaychung]

非常感谢你的回复，不过这个应该不是问题。

问题是不能在类A里去NEW一个类B
BankCustomer bc = new BankCustomer(userid, username, balance, level);

[zzzjaychung]

我试过不使用VOID，但是会出现一个编译错误：

C:\Documents and Settings\Shaun>javac C:\jakarta-tomcat\webapps\Assignment1\WEB-
INF\classes\mypack\BankCustomer.java
C:\jakarta-tomcat\webapps\Assignment1\WEB-INF\classes\mypack\BankCustomer.java:1
0: invalid method declaration; return type required
public Bankcustomer(int userid, String username, float balance, int leve
l){
^
1 error

[tsingien]

public void Bankcustomer
改成：public void BankCustomer

[tsingien]

错了。构造函数是改成：public BankCustomer(int userid, String username, float balance, int level )

字母B和C都要大写，和你的类同名

[yuanjun_xf]

public class BankCustomer{

private int userid = 1000;
private String username = "New Customer";
private float balance = 0;
private int level = 3;

public void Bankcustomer(int userid, String username, float balance, int level){
this.userid = userid;
this.username = username;
this.balance = balance;
this.level = level;
}
构造函数名应该和类名一致，java是区分大小写的哦！