?
Solved

can I use rs.getString("name") directly instead of strName?

Posted on 2001-08-23
7
Medium Priority
?
373 Views
Last Modified: 2012-05-04
hi everybody,
    I met a problem when I want to access database using Java,the code like the following:
    .......
     public void display(Connection con)
    {
     try{
      String strSQL="select name, age from worker";
      Statement st=con.createStatement();
      ResultSet rs=st.executeQuery(strSQL);
     if(rs.getString("name").trim().equals("tom"))
     {....
     }
    }catch(){}
   }

   the problem is that it will throw nullpointexception if the field name's value  is null.
 if I change the code like this,even the name's value is null, it will not throw nullpointexception:
    .....    
   public void display(Connection con)
    {
     String strName="";
     try{
      String strSQL="select name, age from worker";
      Statement st=con.createStatement();
      ResultSet rs=st.executeQuery(strSQL);
      while(rs.next())
      {
         strName=rs.getString("name");
      }
     if(strName.trim().equals("tom"))
     {....
     }
    }catch(){}
   }

 
 anybody know how to do it if I want do the first situation and I don't hope it throws the nullpointexception even the field's value is null?
  thanks.  
0
Comment
Question by:lisayan
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 3
  • 3
7 Comments
 
LVL 3

Expert Comment

by:sghosh092199
ID: 6419877
Hi!

You definitely need to do a rset.next(). This call allows to browse through the records in a resultset.

In the later case, the rs.next() is returning a false value because the query has not selected any record. So, the 'strName' is not set again and it retains the previous value.

The better way to handle this situation is:

while(rs.next())
     {
        strName=rs.getString("name");
if((strName != null) && strName.trim().equals("tom"))
    {....
    }
   
     }

Hope it helps!


   
0
 
LVL 6

Expert Comment

by:kotan
ID: 6420482
If you make sure that you only need to retrive the first record,

try this,

rs.next(); // should include this.
strName = rs.getString("name") == null ? "" : rs.getString("name");
if (strName.trim().equals("tom"))
{
   ...
}
0
 

Author Comment

by:lisayan
ID: 6422124
thanks,everybody. what I try to do is to use rs.getString("name") directly instead of using strName. because there are many fields in a resultset, I don't want to declare them and I only want to use them when I need them. the code like the following:
  ...
  while(rs.next())
  {
   ....
   if(rs.getString("name").equals("tom")){
      ...
   }
 .....
 instead of like this:
  ...
  while(rs.next())
  {
   ...
   strName=rs.getString("name");//declare it
   ...
   if(strName.equals("tom")){
      ....
   }
0
What does it mean to be "Always On"?

Is your cloud always on? With an Always On cloud you won't have to worry about downtime for maintenance or software application code updates, ensuring that your bottom line isn't affected.

 
LVL 3

Expert Comment

by:sghosh092199
ID: 6422178
That will be fine. In case you are using strName, it will assume different values for each record.

0
 

Author Comment

by:lisayan
ID: 6422347
the problem is that it will throw nullpointexception if name's value is null. if I use strName, even the name's value is null, it will not throw nullpointexception.
0
 
LVL 3

Accepted Solution

by:
sghosh092199 earned 200 total points
ID: 6422423
In that case, you can do the following:

if( (rs.getString("name") != null) && rs.getString("name").equals("tom"))
{
     
}

else
// Null value
0
 

Author Comment

by:lisayan
ID: 6422593
thanks,i got it.
0

Featured Post

VIDEO: THE CONCERTO CLOUD FOR HEALTHCARE

Modern healthcare requires a modern cloud. View this brief video to understand how the Concerto Cloud for Healthcare can help your organization.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

This was posted to the Netbeans forum a Feb, 2010 and I also sent it to Verisign. Who didn't help much in my struggles to get my application signed. ------------------------- Start The idea here is to target your cell phones with the correct…
Java functions are among the best things for programmers to work with as Java sites can be very easy to read and prepare. Java especially simplifies many processes in the coding industry as it helps integrate many forms of technology and different d…
Viewers will learn one way to get user input in Java. Introduce the Scanner object: Declare the variable that stores the user input: An example prompting the user for input: Methods you need to invoke in order to properly get  user input:
Viewers will learn about basic arrays, how to declare them, and how to use them. Introduction and definition: Declare an array and cover the syntax of declaring them: Initialize every index in the created array: Example/Features of a basic arr…
Suggested Courses
Course of the Month7 days, 19 hours left to enroll

765 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question