import java.io.*;

class PasswordException extends Exception {
    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    private int i = 0;

    public PasswordException(final int i) {
        super();
        this.i = i;
    }

    public String getMessage() {
        if (i == 0) {
            return "没有这个用户";
        } else if (i == 1) {
            return "密码错误，请重新输入";
        }
        return " ";
    }
}

public class UserLogin {
    private String userName = "";
    private String password = "";

    public void login() {
        InputStreamReader isr = new InputStreamReader(System.in);
        BufferedReader br = new BufferedReader(isr);
        System.out.println("请输入用户名：");
        try {
            userName = br.readLine();
        } catch (IOException e) {
            e.printStackTrace();
        }
        System.out.println("请输入密码：");
        try {
            password = br.readLine();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public void checkPassword() throws PasswordException {
        if (!userName.equals("administrator")) {
            throw new PasswordException(0);
        } else if (!password.equals("admin")) {
            throw new PasswordException(1);
        }else{
            System.out.println("密码已验证正确");
        }
    }

    public static void main(String[] args) {
        UserLogin app = new UserLogin();
        app.login();
        try {
            app.checkPassword();
        } catch (Exception e) {
            System.out.println(e.getMessage());
        }
    }
}

------解决方案--------------------
没错啊。
Java code

/**
 * 
 */
package cn.luochengor.csdn;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

/**
 * 
 * @Author luochengor
 * @Date Nov 26, 2011
 * @Email luochengor@foxmail.com
 */
@SuppressWarnings("serial")
class PasswordException extends Exception {
    private int i = 0;

    public PasswordException(int i) {
        super();
        this.i = i;
    }

    public String getMessage() {
        if (i == 0) {
            return "没有这个用户";
        } else if (i == 1) {
            return "密码错误，请重新输入";
        }
        return " ";
    }
}

public class UserLogin {
    private String userName = "";
    private String password = "";

    public void login() {
        InputStreamReader isr = new InputStreamReader(System.in);
        BufferedReader br = new BufferedReader(isr);
        System.out.println("请输入用户名：");
        try {
            userName = br.readLine();
        } catch (IOException e) {
            System.out.println("输入被中断");
        }
        System.out.println("请输入密码：");
        try {
            password = br.readLine();
        } catch (IOException e) {
            System.out.println("输入被中断");
        }
    }

    public void checkPassword() throws PasswordException {
        if (!userName.equals("administrator")) {
            throw (new PasswordException(0));
        } else if (!password.equals("admin")) {
            throw (new PasswordException(1));
        }
    }

    public static void main(String[] args) {
        UserLogin app = new UserLogin();
        app.login();
        try {
            app.checkPassword();
            System.out.println("密码已验证正确");
        } catch (Exception e) {
            System.out.println(e.getMessage());
        }
    }
}