Thread: Not A Statement - Java Error

I am trying to compile below code in JDK 1.6 but getting an error "Not a statement" in the below line
File file = new File("/data/userfiles/data/conf/dataConfig.xml"); Since this code has been compiled in previous version like 1.3 and 1.4 version.

Can you please tell me what exactly wrong in this because presence of dataConfig.xml need not be checked in the compile time, it has to be checked only during execution.

Kindly provide me a solution , i have to provide this by tomorrow



Source Code

try
{
if (loglevel != 0)
// writelog("Retrieving configuration");
File file = new File("/data/userfiles/data/conf/dataConfig.xml");
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
Document doc = db.parse(file);
doc.getDocumentElement().normalize();
NodeList nodeLst = doc.getElementsByTagName("Configuration");
String servername;
Node fstNode = nodeLst.item(0);
Element fstElmnt = (Element)fstNode;
NodeList fstNmElmntLst = fstElmnt.getElementsByTagName("Server");
Element fstNmElmnt = (Element)fstNmElmntLst.item(0);
NodeList fstNm = fstNmElmnt.getChildNodes();
servername = ((Node)fstNm.item(0)).getNodeValue();



Element sndElmnt = (Element)fstNode;
NodeList sndNmElmntLst = sndElmnt.getElementsByTagName("Log");
Element sndNmElmnt = (Element)sndNmElmntLst.item(0);
NodeList sndNm = sndNmElmnt.getChildNodes();

String nodeval;
Node mynode = (Node)sndNm.item(0);
nodeval = mynode.getNodeValue().trim();
loglevel = Integer.parseInt(nodeval);



sndElmnt = (Element)fstNode;
sndNmElmntLst = sndElmnt.getElementsByTagName("LogPath");
sndNmElmnt = (Element)sndNmElmntLst.item(0);
sndNm = sndNmElmnt.getChildNodes();


mynode = (Node)sndNm.item(0);
logpath = mynode.getNodeValue().trim();
if (loglevel != 0)
writelog("Log Path: " + logpath);
if (loglevel != 0)
writelog("Server : " + ((Node)fstNm.item(0)).getNodeValue());



return servername;

}
catch (Exception e)
{
writelog("Error in Get Server IP:" + e.toString());
return ("ERROR");
}

This is a compiler error, not an execution error. The error manifestation at compile time does not depend on the value of the expression in the parentheses of the if() statement.

(My setup: java and javac versions 1.6. I don't know what happened with earlier versions.)

The following gives compiler errors regardless of the value of the variable in parentheses (At compile time, it doesn't evaluate the variable values.) Since you commented out the statement after the if(), this is the code that the compiler sees

        if (SomeBooleanExpression)
            File file = new File("whatever");

I mean, even if the compiler didn't barf, that statement couldn't possibly do anything useful, since the variable named "file" would go out of scope immediately after being created.

The following also gives compiler errors: (It's not just some quirk of File objects or any other particular type of variable.)

        if (SomeBooleanExpression)
            int x = 10;

The following does not give compiler errors (assuming SomeBooleanExpression has a defined boolean value):

        if (SomeBooleanExpression)
        { /* No executable statements inside the braces */ }
        File file = new File("whatever"); // Always executed

Perhaps this suggests one possible "fix" that will make the program compilable (and, therefore, executable) so that the assignment can be completed.


Interestingly, the following also does not give compiler errors (assuming SomeBooleanExpression has a defined boolean value), even though the statement inside the block can't possibly do anything useful, and, in fact may be optimized away:

        if (SomeBooleanExpression)
        {
            File file = new File("whatever"); // Won't do anything useful
        }

Of course, in this case, you will get compiler errors after this statement if any subsequent expressions use this "file" variable, since it will not be in scope.

Anyhow...

I'm sure that's not what you had in mind, but I think it's interesting to note that the first part of the compiler phase doesn't look inside the block to see if it does anything useful, but if it's a single useless statement (not inside a {} block) after the if(), the compiler decides not to waste any time trying to create something executable.



Bottom line: I think most experienced programmers recommend that you always use {} braces after if () statements even if you don't need them. Then, if you change the program (maybe by adding print() stuff for debugging or maybe by commenting out things for testing), perhaps you will have a smaller chance of running into trouble.



Cheers,

Z