public class Test {

public List<String> getListWithNull() {

        return null;
}

public List<String> getList() {

        return Collections.emptyList();
}

public Map<String, String> getMap() {

        return Collections.EMPTY_MAP;
}

 public static void main(String[] args) {
    Test test = new Test();

   List<String> strings = test.getList();

        for (String i:strings)
            System.out.println(i);

         if(!strings.isEmpty())
           // do

          List<String> stringnull=test.getListWithNull();

        if(stringnull!=null)
           // do
 }}