// Given `intList` with the following elements: 5, 4, 1, 3, 7, 8
List<Integer> evenList = new ArrayList<>();
for(Integer i: intList) {
  if(i % 2 == 0) {
    evenList.add(i*2);
  }
}
// evenList will have elements 8, 16
/*A Stream is a sequence of elements created from a Collection source. A Stream can be used as input to a pipeline, which defines a set of aggregate operations (methods that apply transformations to a Stream of data). The output of an aggregate operation serves as the input of the next operation (these are known as intermediate operations) until we reach a terminal operation, which is the final operation in a pipeline that produces some non Stream output.*/
List<Integer> evenList = intList.stream()
  .filter((number) -> {return number % 2 == 0;})
  .map( evenNum -> evenNum*2)
  .collect(Collectors.toList());