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Thread: Not A Statement - Java Error

  1. #1
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    Default 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");
    }
    Last edited by shagil.a.gopinath; September 22nd, 2012 at 03:10 AM.


  2. #2
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    Default Re: Not A Statement - Java Error

    Hello shagil.a.gopinath!
    Please edit your post and use the code tags to improve its readability. And also it would help if you provided the full error message.

    A notice on your code;
    if (loglevel != 0)
    .
    .
    .
    You should place the statements that will execute if the condition is true, in the same block (ie inside the same pair of {}'s) The way it is now, only the first statement after if will execute. ie only
    File file = new File("/data/userfiles/data/conf/dataConfig.xml");
    Is this what you want or you want all the statements to execute?
    If it is the latter then you should place in the same block.

    Hope this helps.

  3. #3
    Super Moderator jps's Avatar
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    Default Re: Not A Statement - Java Error

    Quote Originally Posted by andreas90 View Post
    ...The way it is now, only the first statement after if will execute...
    The way it is now, when loglevel != 0, everything will execute.
    When loglevel == 0, everything except the following line will execute:File file = new File("/data/userfiles/data/conf/dataConfig.xml");

  4. #4
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    Default Re: Not A Statement - Java 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
    Last edited by Zaphod_b; September 22nd, 2012 at 12:52 PM.

  5. #5
    Super Moderator pbrockway2's Avatar
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    Default Re: Not A Statement - Java Error

    I think the compiler is less concerned with whether the statement has any effect and more with the fact that the following is just wrong:

    if (loglevel != 0)
        File file = new File("/data/userfiles/data/conf/dataConfig.xml");

    "Every local variable declaration statement is immediately contained by a block." (That's JLS 14.4. Local Variable Declaration Statements). This rule of Java's is a good one for making it crystal clear what the scope of file is. And it is yet another reason to follow Zaphod's advice and use braces with if statements.

    ---

    In fact the assignment comes very close to doing something (if it would compile, that is).

    String filename = ...
    if (loglevel != 0) {
        File file = new File(filename);
    }

    The declaration and assignment looks useless, but it would do something at runtime. Sometimes.

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