Comment on this code please

Question

I would like your comments on this code. Doesn't it have a few oppertunities? I know it's jsp, but question is not directed toward the jsp, just the logic/syntax/etc. How about the == for starters?
<%
          String z_Desc = (((String)hshipTrackSummaryDocList.get("Z_DESC")) == null) ? "" : (String)hshipTrackSummaryDocList.get("Z_DESC");
          if (z_Desc  == "" ) {
     %>
     <%
          }else {
     %>
                  <%=(((String)hshipTrackSummaryDocList.get("Z_DESC")) == null) ? "" : (String)hshipTrackSummaryDocList.get("Z_DESC")%></font>
     <%
     %>

Answer 1

Hi mlovern! This code has several opportunities for "improvement". I noticed that the get("Z_DESC") method is called on hshipTrackSummaryDocList object several times. Each time, it returns the very same value. Hence, in the interests of efficiency, it's a better idea to call it once, save the return value and then use the latter.
Also, I'm not too clear about exactly what you intended to do in the else clause. As it stands, your else clause will cause the JSP to fail.
Be very careful while using the "==" operator while comparing strings. That causes object comparison, not object content comparison. The latter is the required test most of the time. Also, while comparing the contents of the strings, it's better to call the equals() method on the empty string or a constant string. So, if I needed to compare a test value against an empty string or a constant, here's how.
if ( "".equals( testString ) )
   // do something
else if ( SOME_CONSTANT.equals( testString ) )
   // do something
}In the above code, even if testString was null, a runtime exception will not be generated. However, if the equals() method was called on testString and it happened to be null, you'd be looking at an exception.
Here's how I would have written the code you supplied.
String zDescValue = (String) hshipTrackSummaryDocList.get( "Z_DESC" );
if ( zDescValue == null ) zDescValue = "";
if ( "".equals( zDescValue ) )
   // do something useful
else
  // do something else
}I've also come across similar situations. In order not to repeat the same code everywhere, I've wound up writing a couple of utility methods to assign "" to a string if it's null. Here are those methods.
public static String processStringValue( String inputString, String defaultValue )
   return ( inputString == null ? defaultValue : inputString );
public static String processStringValue( String inputString )
   return processStringValue( inputString, "" );
}Finally, you may want to be careful about the code fragments you post. From your post and profile, I can guess where you work. Your employer may or may not care if parts of their code start showing up on the Internet. It's better to create a general piece of code that approximates what you want to convey. However, it's better to be safe than sorry.
Hope this helps!
Cheers!