Hi ,

I have bidirectional one-to-many entity relation ship between two tables say PARENT and CHILD and i am using set TreeSet for storing objects of CHILD table. The problem i am facing is that when i am trying to add the second child to the set i am getting an exception "{Class} cannot be cast to java.lang.Comparable" , also when i am trying to save without adding the second child to the parent set i am able to successfully save both child records and the parent.


{ .....

parent.addTochildren(child1);
child1.setMaster1(parent);

parent.addTochildren(child2);//Exception here and
// successfully saved the records when eliminating the same statement

child2.setMaster1(parent);

.......

}
Can any body suggest solution for this ? Is that problem caused by the usage of TreeSet , then please suggest the correct usage of the same.

Thanks in advance

Regards sajith

Class child1 have to implement the Comparable interface or added a Comparator object to the tree. It's quite simple. In fact the first variant needs You add method compareTo(). See for details
here