Question

I need to add objects to a list (with List semantics) while keeping all objects in the list unique. I figured LinkedHashSet would do, but the “re-insert” clause breaks this:

LinkedHashSet<String>list = new LinkedHashSet<String>();
list.add("a");
list.add("b");
list.add("c");
list.add("a");
list.add("a");
System.out.println (list);

Output from the above is: [a, b, c], not [b, c, a] as I would like it.

Is there any such data-structure in Java which handles this case?

Answer 1

try

    Set<String> set = Collections.newSetFromMap(new LinkedHashMap<String, Boolean>(16, 0.75f, true));
    set.add("a");
    set.add("b");
    set.add("c");
    set.add("a");
    set.add("a");
    System.out.println(set);

output

[b, c, a]