Programming Forums > Application Development > Java

Eric the Red · Apr 5th, 2006, 11:51 PM

Would someone please be able to tell me why i'm getting an error in the blue writting? it states "attempt to use a null pointer" (java.lang.NullPointerException)"

If you need the full code let me know. Do you think that the array is out of bounds or is there something else to the error?

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class CalendarTime
        {
            public long milli;
            public long minute;
            public long rightNow;
            public long rightThen;
            public Calendar Now;
            // contructor
            public CalendarTime ()
            {
                Now = Calendar.getInstance ();
                this.milli = Now.getTimeInMillis (); // contructs current time
                this.minute = this.milli / 60000;
                this.rightNow = this.minute;
                this.rightThen = this.minute + 10; //default is 10 minutes.
            }
            // used to set a different time limit
            public void setTime (int x)
            {
                this.rightThen = (Now.getTimeInMillis () / 60000 + x);
            }
            public long getTimeLeft ()
            {
                return this.rightThen - this.rightNow; // time left
            }
            public long getThen ()
            {
                return this.rightThen;
            }
}
LicenseTime = new CalendarTime [intNumberofLines + 1];
c.print ("time = :" + LicenseTime [intNumberofLines - 1].getThen ());

Mjordan2nd · Apr 5th, 2006, 11:53 PM

LicenseTime [intNumberofLines - 1]has never been initialized.

Eric the Red · Apr 5th, 2006, 11:55 PM

Quote:

Originally Posted by Mjordan2nd

LicenseTime [intNumberofLines - 1]has never been initialized.

sorry i didn't include that. But I have initialized it

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CalendarTime LicenseTime [] = new CalendarTime [intNumberofLines];

titaniumdecoy · Apr 5th, 2006, 11:59 PM

When you create a new array of objects, each index of the array defaults to null. Therefore, you have to initialize each index:

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for (int i = 0; i < intNumberofLines; i++)
    licenseTime[i] = new CalendarTime();

Notice that licenseTime should start with a lowercase letter as it is a variable.

Eric the Red · Apr 6th, 2006, 12:02 AM

From what you told me it works perfect, Thanks!

titaniumdecoy · Apr 6th, 2006, 12:13 AM

If you wanted to, you could add a method like the following to the CalendarTime class:

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private static CalendarTime[] createCalendarTimeArray(int size) {
    CalendarTime[] t = new CalendarTime[size];
    for (int i = 0; i < size; i++)
        t[i] = new CalendarTime();
    return t;
}

You could use it like this:

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CalendarTime[] licenseTime = CalendarTime.createCalendarTimeArray(intNumberofLines);

(This probably isn't a good idea; it was in response to the question you posted previously but erased.)

Eric the Red · Apr 6th, 2006, 12:24 AM

Quote:

Originally Posted by titaniumdecoy

If you wanted to, you could add a method like the following to the CalendarTime class:

(Toggle Plain Text)

private static CalendarTime[] createCalendarTimeArray(int size) {
    CalendarTime[] t = new CalendarTime[size];
    for (int i = 0; i < size; i++)
        t[i] = new CalendarTime();
    return t;
}

You could use it like this:

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CalendarTime[] licenseTime = CalendarTime.createCalendarTimeArray(intNumberofLines);

thanks A lot!

Apr 5th, 2006, 11:51 PM	#1
Eric the Red Hobbyist Programmer Join Date: Feb 2006 Posts: 214 Rep Power: 0	null pointer Would someone please be able to tell me why i'm getting an error in the blue writting? it states "attempt to use a null pointer" (java.lang.NullPointerException)" If you need the full code let me know. Do you think that the array is out of bounds or is there something else to the error? (Toggle Plain Text) class CalendarTime { public long milli; public long minute; public long rightNow; public long rightThen; public Calendar Now; // contructor public CalendarTime () { Now = Calendar.getInstance (); this.milli = Now.getTimeInMillis (); // contructs current time this.minute = this.milli / 60000; this.rightNow = this.minute; this.rightThen = this.minute + 10; //default is 10 minutes. } // used to set a different time limit public void setTime (int x) { this.rightThen = (Now.getTimeInMillis () / 60000 + x); } public long getTimeLeft () { return this.rightThen - this.rightNow; // time left } public long getThen () { return this.rightThen; } } LicenseTime = new CalendarTime [intNumberofLines + 1]; c.print ("time = :" + LicenseTime [intNumberofLines - 1].getThen ()); class CalendarTime { public long milli; public long minute; public long rightNow; public long rightThen; public Calendar Now; // contructor public CalendarTime () { Now = Calendar.getInstance (); this.milli = Now.getTimeInMillis (); // contructs current time this.minute = this.milli / 60000; this.rightNow = this.minute; this.rightThen = this.minute + 10; //default is 10 minutes. } // used to set a different time limit public void setTime (int x) { this.rightThen = (Now.getTimeInMillis () / 60000 + x); } public long getTimeLeft () { return this.rightThen - this.rightNow; // time left } public long getThen () { return this.rightThen; } } LicenseTime = new CalendarTime [intNumberofLines + 1]; c.print ("time = :" + LicenseTime [intNumberofLines - 1].getThen ()); __________________ Death smiles at us all. All a man can do is smile back.

Apr 5th, 2006, 11:53 PM	#2
Mjordan2nd The Supreme Ruler Join Date: May 2004 Location: Houston Posts: 1,476 Rep Power: 6	LicenseTime [intNumberofLines - 1]has never been initialized. __________________ "Every gun that is made, every warship launched, every rocket signifies, in the final sense, a theft from those who hunger and are not fed, from those who are cold and are not clothed. The world in arms is not spending money alone. It is spending the sweat of its laborers, the genius of its scientists, the hopes of its children." - Dwight D. Eisenhower

Apr 5th, 2006, 11:59 PM	#4
titaniumdecoy Expert Programmer Join Date: Nov 2005 Posts: 928 Rep Power: 4	When you create a new array of objects, each index of the array defaults to null. Therefore, you have to initialize each index: (Toggle Plain Text) for (int i = 0; i < intNumberofLines; i++) licenseTime[i] = new CalendarTime(); for (int i = 0; i < intNumberofLines; i++) licenseTime[i] = new CalendarTime(); Notice that licenseTime should start with a lowercase letter as it is a variable.

Apr 6th, 2006, 12:02 AM	#5
Eric the Red Hobbyist Programmer Join Date: Feb 2006 Posts: 214 Rep Power: 0	From what you told me it works perfect, Thanks! __________________ Death smiles at us all. All a man can do is smile back. Last edited by Eric the Red; Apr 6th, 2006 at 12:13 AM.

Apr 6th, 2006, 12:13 AM	#6
titaniumdecoy Expert Programmer Join Date: Nov 2005 Posts: 928 Rep Power: 4	If you wanted to, you could add a method like the following to the CalendarTime class: (Toggle Plain Text) private static CalendarTime[] createCalendarTimeArray(int size) { CalendarTime[] t = new CalendarTime[size]; for (int i = 0; i < size; i++) t[i] = new CalendarTime(); return t; } private static CalendarTime[] createCalendarTimeArray(int size) { CalendarTime[] t = new CalendarTime[size]; for (int i = 0; i < size; i++) t[i] = new CalendarTime(); return t; } You could use it like this: (Toggle Plain Text) CalendarTime[] licenseTime = CalendarTime.createCalendarTimeArray(intNumberofLines); CalendarTime[] licenseTime = CalendarTime.createCalendarTimeArray(intNumberofLines); (This probably isn't a good idea; it was in response to the question you posted previously but erased.) Last edited by titaniumdecoy; Apr 6th, 2006 at 12:24 AM.

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