JAVA : Why use Java Stream ?

Motivation

Understanding why we should use Streams over conventional for loop is critical and it can easily ramp up your coding game.

Problem Statement

• list of employee with id,name and salary
• get all the employee whose salary is above 15
• store it in separate list and print it

Conventional Way of Doing

• Traverse List
• Write if and filter on that
• Store it in separate list
• Print separate list

Code

        for( Employee e:empList) {

            if(e.getSal()>15) {
                richGuys.add(e);
            }
        }

Sysout.out.println(richGuys);

Do this with Stream

List<Employee> richGuys=empList.stream()
                .filter(e -> e.getSal()>15)
                .collect(Collectors.toList());

here we have used filter method and given the method to it that how we wants to filter and then we have used collect method to produce the list out of that stream

• There are bunch of other method in stream and we can combine the methods of stream

Example

filter and sorted --> first filter with sal > 15 and then sort with the salary

        List<Employee> richGuysSorted=empList.stream()
                .filter(e -> e.getSal()>15)
                .sorted(Comparator.comparing(employee -> employee.getSal()))
                .collect(Collectors.toList());

Streams will not modify the original list or data structure