Create a List of unique values in java

In the bellow code was your reference

 LinkedHashSet<String> al=new LinkedHashSet<String>();  
  al.add("guru");  
  al.add("karthik");  
  al.add("raja");  
  al.add("karthik");  

  Iterator<String> itr=al.iterator();  
  while(itr.hasNext()){  
   System.out.println(itr.next());  
  }  

output

guru
karthik
raja

Use LinkedHashSet. It serves as both a List and a Set. It has the uniqueness quality of a set but still remembers the order in which you inserted items to it which allows you to iterate it by order of insertion.

From the Docs:

Hash table and linked list implementation of the Set interface, with predictable iteration order. This implementation differs from HashSet in that it maintains a doubly-linked list running through all of its entries. This linked list defines the iteration ordering, which is the order in which elements were inserted into the set (insertion-order). Note that insertion order is not affected if an element is re-inserted into the set. (An element e is reinserted into a set s if s.add(e) is invoked when s.contains(e) would return true immediately prior to the invocation.)

You can use SortedSet or LinkedHashSet

LinkedHashSet is the best possible way out