H1 : Initialize an ArrayList with Zeroes or Null in Java

Initialize an ArrayList with Zeroes or Null in Java

ArrayLists are a dynamic data structure in Java that allow for resizable arrays. This means that you don’t need to worry about the size of your array as it can be adjusted depending on how much data you need to store. When you create an ArrayList, it needs to be initialized before you can start using it. There are two ways to initialize an ArrayList with either zeroes or null in Java.

Initializing an ArrayList with Zeroes

If you want to initialize an ArrayList with zeroes, one of the simplest solutions is to use the Collections.fill() method. You just need to pass in the list that you want to fill and the value which is the number of zeros. This will set all elements in the ArrayList to zero. Here’s an example of how to do this:

List<Integer> list = new ArrayList<>(); 
Collections.fill(list, 0);

Initializing an ArrayList with Nulls

Initializing an ArrayList with null is a bit different from initializing it with zeroes. The simplest way to do this is to use the Java 8 Stream API to generate a stream of nulls. You can then use the collect() method to convert the stream into a List. Here’s an example of how you can do this:

List<Object> list = Stream.generate(() -> null).limit(10).collect(Collectors.toList());

This code will generate a List with 10 null elements. This is just an example, you can adjust the limit to whatever size list you need.

Conclusion

In this tutorial, we have seen two ways to initialize an ArrayList with either zeroes or null in Java. It’s easy to do this with either the Collections.fill() method or the Stream API. This makes it simple to prepare an ArrayList for use in your program.