UnsupportedOperationException on Collection

Question

While studying the Collection API, we find that some methods (add, remove,...) may throw a java.lang.UnsupportedOperationException

Answer 1

Normally when you create a list like List sample=Collections.emptyList();. The List sample will be created as a Collections.unmodifiableCollection().

• So the list sample does not support dynamic list operations. You can only assign another list to this list using assignment operator. Eg>

  List ls=new ArrayList();
  ls.add("one");
  ls.add("Three");
  ls.add("two");
  ls.add("four"); 
  sample = ls;
  

• For dynamic list operations you should have a syntax like List sample= new ArrayList();. In this list you can perform sample.add(), sample.addAll() etc...