Sample case:
class Test {
    final Set<String> uniqueNames = new HashSet<String>();
}
But w/ the help of a plugin can generate methods like this (similar to Generate getters/setters)
class Test {
    final Set<String> uniqueNames = new HashSet<String>();
    public boolean add(String name) {
     return uniqueNames.add(name);
    }
    public boolean remove(Object name) {
     return uniqueNames.remove(name);
    }
}