Want non duplicate elements from list

Question

From following list I need only 'wow' and 'quit'.

List<String> list = new ArrayList();                
list.add("test");       
list.add("test");                   
list.add("wow");    
list.add("quit");
list.add("tree");
list.add("tree");

Answer 1

you can check the frequency of an element in the Collection and rule out the elements which have frequency higher than 1.

   List<String> list = new ArrayList<String>();
    list.add("test");       
    list.add("test");                   
    list.add("wow");    
    list.add("quit");
    list.add("tree");
    list.add("tree");
    for(String s: list){
        if(Collections.frequency(list, s) == 1){
            System.out.println(s);
        }

Output:

wow
quit

Answer 2

This snippet should leave you with a set (output) which contains only non-duplicated elements of your list.

HashSet<String> temp = new HashSet<String>();
HashSet<String> output = new HashSet<String>();

for (String element : list)
{
    if (temp.contains(element)) output.remove(element);
    else
    {
        temp.insert(element);
        output.insert(element);
    }
}

Operates in O(n*log(n)) time: one set of logarithmic operations (set lookups, inserts, etc) for each of the n elements in the list.