[macosxnerd101]

Since your return statement is in your else block, your method may not return anything. However, since you're method is declared with a non-void return type, you must make sure your method returns a value (in this case, an int). If you want to return a flag to signify an invalid input, you could return a negative value (maybe in your if statement).

[sarmanu]

Because you initialize "count" inside the "else". If the "if" executes, then the message of "Error" is printed, and "count" is returned. "count" being not initialized, then a garbage value is returned (probably something like -231020301 ...). Just initialize "count" to 0 when you declare it:

int count = 0;

In this way, when month is lower than 1 or bigger than 12, 0 is returned.

This post has been edited by sarmanu: 23 March 2010 - 10:21 AM

[japanir]

global variables are initialized automatically by the compiler.
int global variables are initialized to 0.
local variables do not.
attemoting such code:

public class Test {
   public static void main(String[] args){
       int localInt;
       System.out.println(localInt);
   }
}

will give you an error.

However this code:

public class Test {
   static int globalInt;
   public static void main(String[] args){
       System.out.println(globalInt);
   }
}

will print 0.

In your case, you assign count with a value only inside the else block.
what happens if the if statement is true? count will never get a value!
and you will not be able to use it later in that method.
as sarmanu said, better initiate count when declaring it.

int count = -1;

you can initiate it to -1, so if the method returns -1, you know that there was an error with the month parameter.

This post has been edited by japanir: 23 March 2010 - 10:49 AM

[japanir]

apparently one of the Objects you refer to in this method is null.
but It is really hard to say without looking at the rest of your code..

[japanir]

you didn't initialized removedMembers.
now it is null.
you cannot call methods from a null object.
you should add this:

ArrayList<Membership>removedMembers = new ArrayList<Membership>();

[macosxnerd101]

Can you tell us what line number it is on and provide the error message? I'm guessing that you have a null reference in your ArrayList some how, or that one of your ArrayLists wasn't properly initialized.

[Dogstopper]

Well, you can throw an exception...Personally, I like IllegalArgumentException as it describes your needs best. Also, instead of System.out.println(), use System.err.println(), as it is the error stream:

    public int joinedInMonth(int month) throw IllegalArgumentException
    {
        int count = 0;
        if(month <1 || month > 12){
            System.err.println("Error");
            throw new IllegalArgumentException("Month must be between 1 and 12 inclusive.");
        }else{
            for(Membership x : clubMembership){
                if(x.getMonth() == month)
                    count ++;
            }
        }
        return count;
    }