How to create a list by iterating two different type of list, using java lambda expressions?

Question

How can i change following code using java 8 lambda expressions. Below is my code:

public class Main {
class Student {
            String name;
            int mark;
            String parentName; 

            public String getName() {
                return name;
            }
            public int getMark() {
                return mark;
            }
            public String getParentName() {
                return parentName;
            }
        }

        class Empl {
            String name;
            long salary;
            String managerName;

            public String getName() {
                return name;
            }
            public long getSalary() {
                return salary;
            }
            public String getManagerName() {
                return managerName;
            }
        }

        public static void main(String[] args) {
            List<Student> list1 = new ArrayList<>();
            List<Empl> list2 = new ArrayList<>();
            // Storing data to list1 and list2
            List<String> result = new ArrayList<>();
            for(Student s :list1) {
                result.add(s.getName());
                result.add(s.getParentName());
            }
            for(Empl m :list2) {
                result.add(m.getName());
                result.add(m.getManagerName());
            }
            System.out.println(result);     
        }
    }

In the above code i have used for loops for adding elements from two different lists. How can i use lamba expressions to perform the same steps above?

That code does nothing. list1 and list2 are empty

bichito
– bichito

2017-03-07 13:51:03 +00:00
Commented Mar 7, 2017 at 13:51 — bichito
– bichito, Commented Mar 7, 2017 at 13:51

Markus Benko · Accepted Answer · 2017-03-07 13:53:34Z

2

The following code does the same:

List<String> result = Stream.concat(
        list1.stream().flatMap(s -> Stream.of(s.getName(), s.getParentName())),
        list2.stream().flatMap(m -> Stream.of(m.getName(), m.getManagerName()))
        )
        .collect(Collectors.toList());

If you need to make sure that an ArrayList is created just use Collectors.toCollection(ArrayList::new) instead.

answered Mar 7, 2017 at 13:53

Markus Benko

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1 Comment

junsid Over a year ago

Thanks Benko, if i want to store parentName to another list. How we can do this on same code ?

zsmb13 · Accepted Answer · 2017-03-07 13:51:17Z

1

I'm not quite sure, but is this what you're looking for?

list1.forEach(s -> {
    result.add(s.getName());
    result.add(s.getParentName());
});
list2.forEach(m -> {
    result.add(m.getName());
    result.add(m.getManagerName());
});

answered Mar 7, 2017 at 13:51

zsmb13

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