This week's book giveaway is in the Jython/Python forum.
We're giving away four copies of Murach's Python Programming and have Michael Urban and Joel Murach on-line!
See this thread for details.
Win a copy of Murach's Python Programming this week in the Jython/Python forum!
  • Post Reply Bookmark Topic Watch Topic
  • New Topic

Run Time Error  RSS feed

 
Frances Hollis
Greenhorn
Posts: 17
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
OK I got my code to compile but I am getting RTE. I would appreciate if someone could give me some help. I am probably overlooking something simple because I do not have a good understanding of using the methods for Collections yet. I am still learning how to read the APIs.




Exception in thread "main" java.lang.NullPointerException
at java.util.TreeMap.compare(TreeMap.java:1093)
at java.util.TreeMap.getEntry(TreeMap.java:347)
at java.util.TreeMap.containsKey(TreeMap.java:204)
at java.util.TreeSet.contains(TreeSet.java:196)
at Roster.find(Roster.java:31)
at RosterTest.doFind(RosterTest.java:69)
at RosterTest.main(RosterTest.java:24)
Press any key to continue . . .
 
fred rosenberger
lowercase baba
Bartender
Posts: 12440
42
Chrome Java Linux
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
a NullPointerExeption comes when you have a reference to an object, but no actual object has been created.

i'm guessing your trying to read something out of your Roster before you put something into it?
 
Prabhu Venkatachalam
Ranch Hand
Posts: 502
Java jQuery Spring
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator


In your Student class, you are implementing compareTo method from Comparable interface. In that method, without checking whether supplied object is null or not, you are calling the method.

Try changing this like below,

 
  • Post Reply Bookmark Topic Watch Topic
  • New Topic
Boost this thread!