Java 8 stream operations execution order

Question

List numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8);
List twoEvenSquares = numbers.stream().filter(n -> {
    System.out.println(\"         


        

Answer 1

The behavior you noticed is the correct one. In order to find out if a number passes the entire Stream pipeline, you have to run that number through all the pipeline steps.

filtering 1 // 1 doesn't pass the filter
filtering 2 // 2 passes the filter, moves on to map
mapping 2 // 2 passes the map and limit steps and is added to output list
filtering 3 // 3 doesn't pass the filter
filtering 4 // 4 passes the filter, moves on to map 
mapping 4 // 4 passes the map and limit steps and is added to output list

now the pipeline can end, since we have two numbers that passed the pipeline.