Design Patterns and Best Practices in Java

Working with collections versus working with streams

Everyone working with Java is aware of collections. We use collections in an imperative way: we tell the program how to do what it's supposed to do. Let's take the following example in which we instantiate a collection of 10 integers, from 1 to 10:

List<Integer> list = new ArrayList<Integer>();for (int i = 0; i < 10; i++){  list.add(i);}

Now, we will create another collection in which we will filter in only the odd numbers:

List<Integer> odds = new ArrayList<Integer>();for (int val : list){  if (val % 2 == 0)  odds.add(val);}

At the end, we want to print the results:

for (int val : odds){  System.out.print(val);}

As you can see, we wrote quite a bit of code to perform three basic operations: ...