useBean 调用类时,遇到异常 ,怎么终止,并返回信息给用户

useBean 调用类时,遇到错误 ,如何终止,并返回信息给用户!
package   com;
import   java.sql.*;
import   db.*;
public   class   newManage
{
ConnDB   con=   new   ConnDB();
private   String   userid,password,qy,username,bm,job,type;

public   void   setUserid(String   u){userid=u;}
public   String   getUserid(){return   userid;}

public   void   setPassword(String   p){password=p;}
public   String   getPassword(){return   password;}

public   void   setQy(String   q){qy=q;}
public   String   getQy(){return   qy;}

public   void   setUsername(String   n){username=n;}
public   String   getUsername(){return   username;}

public   void   setBm(String   b){bm=b;}
public   String   getBm(){return   bm;}

public   void   setJob(String   j){job=j;}
public   String   getJob(){return   job;}

public   void   setType(String   t){type=t;}
public   String   getType(){return   type;}

/***********************************************************************
  *函   数   名:updateDatabase  
  *功能描述:添加管理员帐号
  ***********************************************************************/
public   void   updateDatabase(){

//定义链接的conn对象
Connection   conn=null;

try   {
//     打开数据库连接
conn=con.mygetConn();

//     数据判断
if   (userid!=null)
userid   =   new   String(userid.getBytes( "ISO-8859-1 "),   "GBK ");
else
userid= "未知 ";

if   (qy!=null)  
qy   =   new   String(qy.getBytes( "ISO-8859-1 "),   "GBK ");
else
qy= "未知 ";

if   (job!=null)  
job   =   new   String(job.getBytes( "ISO-8859-1 "),   "GBK ");
else
job= "未知 ";

if   (bm!=null)  
bm   =   new   String(bm.getBytes( "ISO-8859-1 "),   "GBK ");
else
bm= "未知 ";

if   (username!=null)  
username   =   new   String(username.getBytes( "ISO-8859-1 "),   "GBK ");
else
username= "未知 ";

if   ( "1 ".equals(type)){}else{type= "0 ";}

//检查帐号是否重复
String   clickSql= "Select   userid   From   Manages   Where   userid=? ";
PreparedStatement   perstmt=conn.prepareStatement(clickSql);;
perstmt.setString(1,userid);
ResultSet   rs=perstmt.executeQuery();
if(rs.next()){
System.out.print( "对不起,帐号重复了! ");
}else{
//添加管理员信息
String   sql= "Insert   Into   Manages(userid,[password],qy,username,job,bm,type)   values(?,?,?,?,?,?,?) ";
perstmt=conn.prepareStatement(sql);

perstmt.setString(1,userid);
perstmt.setString(2,password);
perstmt.setString(3,qy);
perstmt.setString(4,username);
perstmt.setString(5,job);
perstmt.setString(6,bm);
perstmt.setString(7,type);
perstmt.executeUpdate();
System.out.print( "成功添加管理员信息! ");

}

perstmt=null;
rs=null;


}catch(Exception   e)   {

e.printStackTrace();
}
}
}

当帐号重复时,如何终止程序,并返回信息给用户,弹出对话框,告诉用户帐号重复,并返回到上一页!

[解决办法]
import java.sql.*;

public class newManage {

ConnDB con = new ConnDB();

private String userid, password, qy, username, bm, job, type;

public void setUserid(String u) {
userid = u;
}

public String getUserid() {
return userid;
}

public void setPassword(String p) {
password = p;
}

public String getPassword() {
return password;
}

public void setQy(String q) {
qy = q;
}

public String getQy() {
return qy;
}

public void setUsername(String n) {
username = n;
}

public String getUsername() {
return username;
}

public void setBm(String b) {
bm = b;
}

public String getBm() {
return bm;
}

public void setJob(String j) {
job = j;
}

public String getJob() {
return job;
}

public void setType(String t) {
type = t;
}

public String getType() {
return type;
}

/***************************************************************************
* 函 数 名:updateDatabase 功能描述:添加管理员帐号
**************************************************************************/
public String updateDatabase() {

// 定义链接的conn对象
Connection conn = null;
PreparedStatement perstmt = null;

try {
// 打开数据库连接
conn = con.mygetConn();

if (! "1 ".equals(type)) {
type = "0 ";
}

// 检查帐号是否重复
String clickSql = "Select userid From Manages Where userid=? ";
perstmt = conn.prepareStatement(clickSql);
perstmt.setString(1, userid);
ResultSet rs = perstmt.executeQuery();
int i = 0;
if (rs.next()) {
System.out.print( "对不起,帐号重复了! ");
return "帐号重复 ";
}

// 添加管理员信息
String sql = "Insert Into Manages(userid,password,qy,username,job,bm,type) values(?,?,?,?,?,?,?) ";
perstmt = conn.prepareStatement(sql);
perstmt.setString(1, getUserid());
perstmt.setString(2, getPassword());
perstmt.setString(3, getQy());
perstmt.setString(4, getUsername());
perstmt.setString(5, getJob());
perstmt.setString(6, getBm());
perstmt.setString(7, getType());
i = perstmt.executeUpdate();
if (i == 1)
System.out.print( "成功添加管理员信息! ");
else
System.out.print( "添加管理员信息失败! ");
rs.close();
perstmt.close();
return "OK ";

} catch (Exception e) {
e.printStackTrace();
}
return "BAD ";
}

public static void main(String args[]) {
newManage mm = new newManage();
mm.setBm( "方法 ");
mm.setJob( "方法 ");
mm.setPassword( "方法 ");
mm.setQy( "方法 ");
mm.setType( "方法 ");
mm.setUserid( "方法 ");
mm.setUsername( "方法 ");
String info = mm.updateDatabase();
System.out.println(info);
}
}