Then you need a ArrayList of ArrayLists: ArrayList<ArrayList<String>> nodes = new ArrayList<ArrayList<String>>(); ArrayList<String> nodeList = new ArrayList<String>(); nodes.add(nodeList); Note that NodeList has been changed to nodeList. In Java Naming Conventions variables start with a lower case. Classes start with an upper case.
But how can we add strings to arraylist whose type has already been specified as Integer? Because of the way Java generics was designed for backwards compatibility, with type erasure and raw types, basically. At execution time, there’s no such things as an ArrayList<Integer> – there’s just an ArrayList. You’re using the raw type List, … Read more
You could iterate backwards and remove as you go through the ArrayList. This has the advantage of subsequent elements not needing to shift and is easier to program than moving forwards.
You don’t need to re-add the ArrayList back to your Map. If the ArrayList already exists then just add your value to it. An improved implementation might look like: Map<String, Collection<String>> map = new HashMap<String, Collection<String>>(); while processing each line: String user = user field from line String value = value field from line Collection<String> … Read more
Welcome to a world with Java 8! It only took me all night with no sleep to learn what was needed to write this one freaking line of code. I’m sure it is already out there somewhere but I couldn’t find it. So I’m sharing my hours and hours of research, enjoy. Woot! Assuming: ArrayList<ArrayList<String>> … Read more
An alternative option is to use Powershell’s ability to assign multiple variables (see this other answer). $arr = 1..5 $first, $rest= $arr $rest 2 3 4 5 It’s been a feature of Powershell for over a decade. I found this functionality from an MSDN blog post:
Another way to go is: Collections.sort(abc, new Comparator<Abc>() { @Override public int compare(Abc abc1, Abc abc2) { return Boolean.compare(abc2.isClickable,abc1.isClickable); } });
ArrayList remove() relies on the objects implementation of the Equal method. If no implementation has been done then the object is removed by Object‘s implementation of Equals which indeed is the pointer comparison. From the documentation on ArrayList – More formally, removes the element with the lowest index i such that (o==null ? get(i)==null : … Read more