Adding a non-comparable (any object that doesn’t implement Comparable) object in a TreeSet or TreeMap object. What to remember about sorting with Java Use Comparable when the comparison is ...

Learn how to implement the equals and hashCode methods in Java to ensure consistent and logical object equality in object-oriented design. Skip to main content LinkedIn Articles ...

Java Collection means a single unit of objects. Java Collection framework provides many interfaces (Set, List, Queue, Deque) and classes (ArrayList, Vector, LinkedList, PriorityQueue, ... Java TreeMap ...

My best guess to what was causing this is that your TreeMap contained non-static inner class instances and that your outer class wasn't serializable or it contained a member that wasn't.

Java Collection means a single unit of objects. Java Collection framework provides many interfaces (Set, List, Queue, Deque) and classes (ArrayList, Vector, LinkedList, PriorityQueue, ... Java TreeMap ...