// ArrayList tourists

for (Tourist t : tourists) {
    if (t != null) {
        t.setId(idForm);
    }
}

tourists.removeAll(Collections.singleton(null));

list.removeAll(Collections.singleton(null));

public static String[] clean(final String[] v) {
    List<String> list = new ArrayList<String>(Arrays.asList(v));
    list.removeAll(Collections.singleton(null));
    return list.toArray(new String[list.size()]);
}

while(tourists.remove(null));

for (Iterator<Tourist> itr = tourists.iterator(); itr.hasNext();) {
      if (itr.next() == null) { itr.remove(); }
 }

ImmutableList.copyOf(Iterables.filter(tourists, Predicates.notNull()))

List s1=new ArrayList();
s1.add(null);

yourCollection.removeAll(s1);

tourists.removeAll(Arrays.asList(null));

tourists.removeAll(Arrays.asList("null"));