Java 8 List into Map

Question

I want to translate a List of objects into a Map using Java 8\'s streams and lambdas.

This is how I would write it in Java 7 and below.

private Map&l         


        

Answer 1

This can be done in 2 ways. Let person be the class we are going to use to demonstrate it.

public class Person {

    private String name;
    private int age;

    public String getAge() {
        return age;
    }
}

Let persons be the list of Persons to be converted to the map

1.Using Simple foreach and a Lambda Expression on the List

Map> mapPersons = new HashMap<>();
persons.forEach(p->mapPersons.put(p.getAge(),p));

2.Using Collectors on Stream defined on the given List.

 Map> mapPersons = 
           persons.stream().collect(Collectors.groupingBy(Person::getAge));