Carey Brown

Just to clarify a few things. You don't need to assign the difference to a variable named "timeDifference" in order to be in sync with the calling code. You could name it anything you want here and it wouldn't impact the caller. In fact, you don't need any variable at all, you can just return it like this:
  public long findDifference(String start_date, String end_date) throws ParseException    {        // SimpleDateFormat converts the string format to date object        SimpleDateFormat sdf = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss");                 // parse method is used to parse the text from a string to produce the date              Date d1 = sdf.parse(start_date);              Date d2 = sdf.parse(end_date);                // Calculate time difference in milliseconds            return d2.getTime() - d1.getTime();    } Similarly, the name of your parameter "start_date" doesn't need to match the name used in the calling code. You could have named it anything you wanted here with no impact to the caller.

Note that you are currently not doing anything if an exception is thrown. I suggest you fix this ASAP.

You have a couple of ways to address the issue:
Move the code inside the try block.
try {            long timeDifference = findDifference( start_date, end_date );            System.out.println("timeDifference2 " + timeDifference);                        double timeDiff = (double)timeDifference;            double _10MinsTimeDifference = Math.round(timeDiff / 60.0);            System.out.println("_10MinsTD " + _10MinsTimeDifference);        } catch( ParseException ex ) {            // do something with exception        }Declare "timeDifference" outside the try block.
long timeDifference = 0; try {            timeDifference = findDifference( start_date, end_date );            System.out.println("timeDifference2 " + timeDifference);        } catch( ParseException ex ) {            // do something with exception        }            double timeDiff = (double)timeDifference;        double _10MinsTimeDifference = Math.round(timeDiff / 60.0);        System.out.println("_10MinsTD " + _10MinsTimeDifference);

Bob Matthews wrote:try {    long timeDifference = findDifference( start_date, end_date );    System.out.println("timeDifference2 " + timeDifference); } catch( ParseException ex ) {    // do something with exception } double timeDiff = (double)timeDifference; double _10MinsTimeDifference = Math.round(timeDiff / 60.0); System.out.println("_10MinsTD " + _10MinsTimeDifference); ..........

Remember what I said about the "scope" of variables? On line 2 you have "timeDifference" inside the scope of a try block. On line 9 you have the same variable name but in a different scope. They can't be the same variable.

Hope everything's ok now. I'm calling it a night.

Bob Matthews wrote:long timeDifference = Timedifferences.findDifference( start_date, end_date ); should I replace timeDifference with difference_In_Time ?

Doesn't matter what you call it but lines 5 and 7 must match.

Bob Matthews wrote:No - the method timeDifferences is not in a file called timeDifferences.java

Then that means you probably have an inner class. Is it defined INSIDE the definition of another class?

Right now your "Timedifferences" class has only one method that should be static but because it is not defined as a top-level class the compiler is complaining. You might want to move the findDifference method out to your top-level class so that static is not a problem and then call it using just findDifference(...) with no Timedifferences in front.

Is class "Timedifferences" defined inside a file named "Timedifferences.java" ?

Bob Matthews wrote:String start_date = (testEvents[k].startDate + testEvents[k].startTime); String end_date = (testEvents[k].endDate + testEvents[k].endTime); try {    long timeDifference = Timedifferences.findDifference( start_date, end_date );    System.out.println("timeDiff " + difference_In_Time); } catch( ParseException ex ) {    // do something with exception }

Bob, it's hard for me to stay in sync with you and the changes you're making.  In this post when you call findDifference() it is assigning it to "timeDifference". It knows nothing of what the variable may have been named inside the method.

Bob Matthews wrote:long difference_In_Time = d2.getTime() - d1.getTime();

difference_In_Time = findDifference    

You may have two variables declared in your code with the same name but that doesn't mean that they are the same variable. It depends on the "scope" of the variable. "difference_In_Time" in your method is "local" to that method only.

Ah. Is your Timedifferences class an inner class?

Show me the code and show me the error message.

Bob Matthews wrote:new error:

cannot make a static reference to the non-static method findDifference(String, String) from the type TimeDifferences

String start_date = (testEvents[k].startDate + testEvents[k].startTime); String end_date = (testEvents[k].endDate + testEvents[k].endTime); try {    long timeDifference = Timedifferences.findDifference( start_date, end_date );    System.out.println("timeDiff " + difference_In_Time); } catch( ParseException ex ) {    // do something with exception }

You are loading one variable on line 5 but printing a different one on line 7.

Carey Brown wrote:I don't know what your full intentions were for the "timedifferences" class but as it stands right now it looks like a utility class. So the method findDifference() doesn't really require that there be an object so it should be declared "static".

Bob Matthews wrote:calling code...........
try {    long timeDifference = Timedifferences.findDifference( startDate, endDate );    System.out.println("timeDiff " + difference_In_Time); } catch( ParseException ex ) {    // do something with exception }
error: the method findDifference(String, String) is not applicable for the arguments (Date,Date)

You are  trying to print "difference_In_Time" but that variable is not part of this method. The variable you've declared here is "timeDifference".

Java naming conventions say that all variables must begin with a lower case letter and use camel case. The underscore (_) should not be used in variable names but can be used in constant names.